diff --git a/.travis.yml b/.travis.yml
index 5c4725f..871d4e3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,58 +1,58 @@
 language: python
-sudo: required
+cache: pip
 dist: xenial
 
-python:
-  - 2.7
-  - 3.4
-  - 3.5
-  - 3.6
-  - 3.7
-
-env:
-  matrix:
-    - DJANGO=1.11
-    - DJANGO=2.1
-    - DJANGO=2.2
-    - DJANGO=master
-
 install:
-  - TOX_ENV=py${TRAVIS_PYTHON_VERSION}-django${DJANGO}
-  - pip install tox
-  - tox -e $TOX_ENV --notest
-script:
-  - tox -e $TOX_ENV
+  - pip install tox tox-travis
 
-after_success:
-  - tox -e $TOX_ENV -- pip install coveralls 
-  - tox -e $TOX_ENV -- coveralls $COVERALLS_OPTION
+script: 
+  - tox
+
+after_success: 
+  - pip install coveralls
+  - coveralls
 
 matrix:
   fast_finish: true
   include:
-  - python: 3.5
-    script: tox -e lint
-  exclude:
     - python: 2.7
-      env: DJANGO=2.1
-    - python: 2.7
-      env: DJANGO=2.2
-    - python: 2.7
-      env: DJANGO=master
-    - python: 3.4
-      env: DJANGO=2.1
-    - python: 3.4
-      env: DJANGO=2.2
-    - python: 3.4
-      env: DJANGO=master
+      env: DJANGO=1.11
+
     - python: 3.5
+      env: DJANGO=1.11
+    - python: 3.5
+      env: DJANGO=2.0
+    - python: 3.5
+      env: DJANGO=2.1
+    - python: 3.5
+      env: DJANGO=2.2
+
+    - python: 3.6
+      env: DJANGO=1.11
+    - python: 3.6
+      env: DJANGO=2.0
+    - python: 3.6
+      env: DJANGO=2.1
+    - python: 3.6
+      env: DJANGO=2.2
+    - python: 3.6
       env: DJANGO=master
-    - python: 3.7
-      env: DJANGO=1.10
+
     - python: 3.7
       env: DJANGO=1.11
-  allow_failures:
     - python: 3.7
+      env: DJANGO=2.0
+    - python: 3.7
+      env: DJANGO=2.1
+    - python: 3.7
+      env: DJANGO=2.2
+    - python: 3.7
+      env: DJANGO=master
+
+    - python: 3.7
+      env: TOXENV=black,flake8
+
+  allow_failures:
     - env: DJANGO=master
 
 deploy:
diff --git a/Makefile b/Makefile
index 061ad4e..70badcb 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@ tests:
 	py.test graphene_django --cov=graphene_django -vv
 
 format:
-	black graphene_django
+	black --exclude "/migrations/" graphene_django examples
 
 lint:
-	flake8 graphene_django
+	flake8 graphene_django examples
diff --git a/examples/cookbook-plain/cookbook/ingredients/admin.py b/examples/cookbook-plain/cookbook/ingredients/admin.py
index b57cbc3..042682f 100644
--- a/examples/cookbook-plain/cookbook/ingredients/admin.py
+++ b/examples/cookbook-plain/cookbook/ingredients/admin.py
@@ -5,8 +5,8 @@ from cookbook.ingredients.models import Category, Ingredient
 
 @admin.register(Ingredient)
 class IngredientAdmin(admin.ModelAdmin):
-    list_display = ('id', 'name', 'category')
-    list_editable = ('name', 'category')
+    list_display = ("id", "name", "category")
+    list_editable = ("name", "category")
 
 
 admin.site.register(Category)
diff --git a/examples/cookbook-plain/cookbook/ingredients/apps.py b/examples/cookbook-plain/cookbook/ingredients/apps.py
index 21b4b08..3ad0143 100644
--- a/examples/cookbook-plain/cookbook/ingredients/apps.py
+++ b/examples/cookbook-plain/cookbook/ingredients/apps.py
@@ -2,6 +2,6 @@ from django.apps import AppConfig
 
 
 class IngredientsConfig(AppConfig):
-    name = 'cookbook.ingredients'
-    label = 'ingredients'
-    verbose_name = 'Ingredients'
+    name = "cookbook.ingredients"
+    label = "ingredients"
+    verbose_name = "Ingredients"
diff --git a/examples/cookbook-plain/cookbook/ingredients/models.py b/examples/cookbook-plain/cookbook/ingredients/models.py
index 5836949..5d88785 100644
--- a/examples/cookbook-plain/cookbook/ingredients/models.py
+++ b/examples/cookbook-plain/cookbook/ingredients/models.py
@@ -3,7 +3,8 @@ from django.db import models
 
 class Category(models.Model):
     class Meta:
-        verbose_name_plural = 'Categories'
+        verbose_name_plural = "Categories"
+
     name = models.CharField(max_length=100)
 
     def __str__(self):
@@ -13,7 +14,9 @@ class Category(models.Model):
 class Ingredient(models.Model):
     name = models.CharField(max_length=100)
     notes = models.TextField(null=True, blank=True)
-    category = models.ForeignKey(Category, related_name='ingredients', on_delete=models.CASCADE)
+    category = models.ForeignKey(
+        Category, related_name="ingredients", on_delete=models.CASCADE
+    )
 
     def __str__(self):
         return self.name
diff --git a/examples/cookbook-plain/cookbook/ingredients/schema.py b/examples/cookbook-plain/cookbook/ingredients/schema.py
index e7ef688..1a54c4b 100644
--- a/examples/cookbook-plain/cookbook/ingredients/schema.py
+++ b/examples/cookbook-plain/cookbook/ingredients/schema.py
@@ -15,14 +15,12 @@ class IngredientType(DjangoObjectType):
 
 
 class Query(object):
-    category = graphene.Field(CategoryType,
-                              id=graphene.Int(),
-                              name=graphene.String())
+    category = graphene.Field(CategoryType, id=graphene.Int(), name=graphene.String())
     all_categories = graphene.List(CategoryType)
 
-    ingredient = graphene.Field(IngredientType,
-                                id=graphene.Int(),
-                                name=graphene.String())
+    ingredient = graphene.Field(
+        IngredientType, id=graphene.Int(), name=graphene.String()
+    )
     all_ingredients = graphene.List(IngredientType)
 
     def resolve_all_categories(self, context):
@@ -30,7 +28,7 @@ class Query(object):
 
     def resolve_all_ingredients(self, context):
         # We can easily optimize query count in the resolve method
-        return Ingredient.objects.select_related('category').all()
+        return Ingredient.objects.select_related("category").all()
 
     def resolve_category(self, context, id=None, name=None):
         if id is not None:
diff --git a/examples/cookbook-plain/cookbook/ingredients/tests.py b/examples/cookbook-plain/cookbook/ingredients/tests.py
index 4929020..a39b155 100644
--- a/examples/cookbook-plain/cookbook/ingredients/tests.py
+++ b/examples/cookbook-plain/cookbook/ingredients/tests.py
@@ -1,2 +1 @@
-
 # Create your tests here.
diff --git a/examples/cookbook-plain/cookbook/ingredients/views.py b/examples/cookbook-plain/cookbook/ingredients/views.py
index b8e4ee0..60f00ef 100644
--- a/examples/cookbook-plain/cookbook/ingredients/views.py
+++ b/examples/cookbook-plain/cookbook/ingredients/views.py
@@ -1,2 +1 @@
-
 # Create your views here.
diff --git a/examples/cookbook-plain/cookbook/recipes/apps.py b/examples/cookbook-plain/cookbook/recipes/apps.py
index 1f24f13..f1e4dde 100644
--- a/examples/cookbook-plain/cookbook/recipes/apps.py
+++ b/examples/cookbook-plain/cookbook/recipes/apps.py
@@ -2,6 +2,6 @@ from django.apps import AppConfig
 
 
 class RecipesConfig(AppConfig):
-    name = 'cookbook.recipes'
-    label = 'recipes'
-    verbose_name = 'Recipes'
+    name = "cookbook.recipes"
+    label = "recipes"
+    verbose_name = "Recipes"
diff --git a/examples/cookbook-plain/cookbook/recipes/models.py b/examples/cookbook-plain/cookbook/recipes/models.py
index 382b88e..f6e955e 100644
--- a/examples/cookbook-plain/cookbook/recipes/models.py
+++ b/examples/cookbook-plain/cookbook/recipes/models.py
@@ -6,17 +6,23 @@ from ..ingredients.models import Ingredient
 class Recipe(models.Model):
     title = models.CharField(max_length=100)
     instructions = models.TextField()
+
     def __str__(self):
         return self.title
 
 
 class RecipeIngredient(models.Model):
-    recipe = models.ForeignKey(Recipe, related_name='amounts', on_delete=models.CASCADE)
-    ingredient = models.ForeignKey(Ingredient, related_name='used_by', on_delete=models.CASCADE)
+    recipe = models.ForeignKey(Recipe, related_name="amounts", on_delete=models.CASCADE)
+    ingredient = models.ForeignKey(
+        Ingredient, related_name="used_by", on_delete=models.CASCADE
+    )
     amount = models.FloatField()
-    unit = models.CharField(max_length=20, choices=(
-        ('unit', 'Units'),
-        ('kg', 'Kilograms'),
-        ('l', 'Litres'),
-        ('st', 'Shots'),
-    ))
+    unit = models.CharField(
+        max_length=20,
+        choices=(
+            ("unit", "Units"),
+            ("kg", "Kilograms"),
+            ("l", "Litres"),
+            ("st", "Shots"),
+        ),
+    )
diff --git a/examples/cookbook-plain/cookbook/recipes/schema.py b/examples/cookbook-plain/cookbook/recipes/schema.py
index 74692f8..b029570 100644
--- a/examples/cookbook-plain/cookbook/recipes/schema.py
+++ b/examples/cookbook-plain/cookbook/recipes/schema.py
@@ -15,13 +15,10 @@ class RecipeIngredientType(DjangoObjectType):
 
 
 class Query(object):
-    recipe = graphene.Field(RecipeType,
-                            id=graphene.Int(),
-                            title=graphene.String())
+    recipe = graphene.Field(RecipeType, id=graphene.Int(), title=graphene.String())
     all_recipes = graphene.List(RecipeType)
 
-    recipeingredient = graphene.Field(RecipeIngredientType,
-                                      id=graphene.Int())
+    recipeingredient = graphene.Field(RecipeIngredientType, id=graphene.Int())
     all_recipeingredients = graphene.List(RecipeIngredientType)
 
     def resolve_recipe(self, context, id=None, title=None):
@@ -43,5 +40,5 @@ class Query(object):
         return Recipe.objects.all()
 
     def resolve_all_recipeingredients(self, context):
-        related = ['recipe', 'ingredient']
+        related = ["recipe", "ingredient"]
         return RecipeIngredient.objects.select_related(*related).all()
diff --git a/examples/cookbook-plain/cookbook/recipes/tests.py b/examples/cookbook-plain/cookbook/recipes/tests.py
index 4929020..a39b155 100644
--- a/examples/cookbook-plain/cookbook/recipes/tests.py
+++ b/examples/cookbook-plain/cookbook/recipes/tests.py
@@ -1,2 +1 @@
-
 # Create your tests here.
diff --git a/examples/cookbook-plain/cookbook/recipes/views.py b/examples/cookbook-plain/cookbook/recipes/views.py
index b8e4ee0..60f00ef 100644
--- a/examples/cookbook-plain/cookbook/recipes/views.py
+++ b/examples/cookbook-plain/cookbook/recipes/views.py
@@ -1,2 +1 @@
-
 # Create your views here.
diff --git a/examples/cookbook-plain/cookbook/schema.py b/examples/cookbook-plain/cookbook/schema.py
index f91d62c..bde9372 100644
--- a/examples/cookbook-plain/cookbook/schema.py
+++ b/examples/cookbook-plain/cookbook/schema.py
@@ -5,10 +5,12 @@ import graphene
 from graphene_django.debug import DjangoDebug
 
 
-class Query(cookbook.ingredients.schema.Query,
-            cookbook.recipes.schema.Query,
-            graphene.ObjectType):
-    debug = graphene.Field(DjangoDebug, name='_debug')
+class Query(
+    cookbook.ingredients.schema.Query,
+    cookbook.recipes.schema.Query,
+    graphene.ObjectType,
+):
+    debug = graphene.Field(DjangoDebug, name="_debug")
 
 
 schema = graphene.Schema(query=Query)
diff --git a/examples/cookbook-plain/cookbook/settings.py b/examples/cookbook-plain/cookbook/settings.py
index bce2bab..7eb9d56 100644
--- a/examples/cookbook-plain/cookbook/settings.py
+++ b/examples/cookbook-plain/cookbook/settings.py
@@ -21,7 +21,7 @@ BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 # See https://docs.djangoproject.com/en/1.9/howto/deployment/checklist/
 
 # SECURITY WARNING: keep the secret key used in production secret!
-SECRET_KEY = '_$=$%eqxk$8ss4n7mtgarw^5$8^d5+c83!vwatr@i_81myb=e4'
+SECRET_KEY = "_$=$%eqxk$8ss4n7mtgarw^5$8^d5+c83!vwatr@i_81myb=e4"
 
 # SECURITY WARNING: don't run with debug turned on in production!
 DEBUG = True
@@ -32,64 +32,61 @@ ALLOWED_HOSTS = []
 # Application definition
 
 INSTALLED_APPS = [
-    'django.contrib.admin',
-    'django.contrib.auth',
-    'django.contrib.contenttypes',
-    'django.contrib.sessions',
-    'django.contrib.messages',
-    'django.contrib.staticfiles',
-    'graphene_django',
-
-    'cookbook.ingredients.apps.IngredientsConfig',
-    'cookbook.recipes.apps.RecipesConfig',
+    "django.contrib.admin",
+    "django.contrib.auth",
+    "django.contrib.contenttypes",
+    "django.contrib.sessions",
+    "django.contrib.messages",
+    "django.contrib.staticfiles",
+    "graphene_django",
+    "cookbook.ingredients.apps.IngredientsConfig",
+    "cookbook.recipes.apps.RecipesConfig",
 ]
 
 MIDDLEWARE = [
-    'django.middleware.security.SecurityMiddleware',
-    'django.contrib.sessions.middleware.SessionMiddleware',
-    'django.middleware.common.CommonMiddleware',
-    'django.middleware.csrf.CsrfViewMiddleware',
-    'django.contrib.auth.middleware.AuthenticationMiddleware',
-    'django.contrib.messages.middleware.MessageMiddleware',
-    'django.middleware.clickjacking.XFrameOptionsMiddleware',
+    "django.middleware.security.SecurityMiddleware",
+    "django.contrib.sessions.middleware.SessionMiddleware",
+    "django.middleware.common.CommonMiddleware",
+    "django.middleware.csrf.CsrfViewMiddleware",
+    "django.contrib.auth.middleware.AuthenticationMiddleware",
+    "django.contrib.messages.middleware.MessageMiddleware",
+    "django.middleware.clickjacking.XFrameOptionsMiddleware",
 ]
 
 GRAPHENE = {
-    'SCHEMA': 'cookbook.schema.schema',
-    'SCHEMA_INDENT': 2,
-    'MIDDLEWARE': (
-        'graphene_django.debug.DjangoDebugMiddleware',
-    )
+    "SCHEMA": "cookbook.schema.schema",
+    "SCHEMA_INDENT": 2,
+    "MIDDLEWARE": ("graphene_django.debug.DjangoDebugMiddleware",),
 }
 
-ROOT_URLCONF = 'cookbook.urls'
+ROOT_URLCONF = "cookbook.urls"
 
 TEMPLATES = [
     {
-        'BACKEND': 'django.template.backends.django.DjangoTemplates',
-        'DIRS': [],
-        'APP_DIRS': True,
-        'OPTIONS': {
-            'context_processors': [
-                'django.template.context_processors.debug',
-                'django.template.context_processors.request',
-                'django.contrib.auth.context_processors.auth',
-                'django.contrib.messages.context_processors.messages',
-            ],
+        "BACKEND": "django.template.backends.django.DjangoTemplates",
+        "DIRS": [],
+        "APP_DIRS": True,
+        "OPTIONS": {
+            "context_processors": [
+                "django.template.context_processors.debug",
+                "django.template.context_processors.request",
+                "django.contrib.auth.context_processors.auth",
+                "django.contrib.messages.context_processors.messages",
+            ]
         },
-    },
+    }
 ]
 
-WSGI_APPLICATION = 'cookbook.wsgi.application'
+WSGI_APPLICATION = "cookbook.wsgi.application"
 
 
 # Database
 # https://docs.djangoproject.com/en/1.9/ref/settings/#databases
 
 DATABASES = {
-    'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
+    "default": {
+        "ENGINE": "django.db.backends.sqlite3",
+        "NAME": os.path.join(BASE_DIR, "db.sqlite3"),
     }
 }
 
@@ -99,26 +96,20 @@ DATABASES = {
 
 AUTH_PASSWORD_VALIDATORS = [
     {
-        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
+        "NAME": "django.contrib.auth.password_validation.UserAttributeSimilarityValidator"
     },
+    {"NAME": "django.contrib.auth.password_validation.MinimumLengthValidator"},
+    {"NAME": "django.contrib.auth.password_validation.CommonPasswordValidator"},
+    {"NAME": "django.contrib.auth.password_validation.NumericPasswordValidator"},
 ]
 
 
 # Internationalization
 # https://docs.djangoproject.com/en/1.9/topics/i18n/
 
-LANGUAGE_CODE = 'en-us'
+LANGUAGE_CODE = "en-us"
 
-TIME_ZONE = 'UTC'
+TIME_ZONE = "UTC"
 
 USE_I18N = True
 
@@ -130,4 +121,4 @@ USE_TZ = True
 # Static files (CSS, JavaScript, Images)
 # https://docs.djangoproject.com/en/1.9/howto/static-files/
 
-STATIC_URL = '/static/'
+STATIC_URL = "/static/"
diff --git a/examples/cookbook-plain/cookbook/urls.py b/examples/cookbook-plain/cookbook/urls.py
index 4f87da0..a64a875 100644
--- a/examples/cookbook-plain/cookbook/urls.py
+++ b/examples/cookbook-plain/cookbook/urls.py
@@ -5,6 +5,6 @@ from graphene_django.views import GraphQLView
 
 
 urlpatterns = [
-    path('admin/', admin.site.urls),
-    path('graphql/', GraphQLView.as_view(graphiql=True)),
+    path("admin/", admin.site.urls),
+    path("graphql/", GraphQLView.as_view(graphiql=True)),
 ]
diff --git a/examples/cookbook/cookbook/ingredients/admin.py b/examples/cookbook/cookbook/ingredients/admin.py
index b57cbc3..042682f 100644
--- a/examples/cookbook/cookbook/ingredients/admin.py
+++ b/examples/cookbook/cookbook/ingredients/admin.py
@@ -5,8 +5,8 @@ from cookbook.ingredients.models import Category, Ingredient
 
 @admin.register(Ingredient)
 class IngredientAdmin(admin.ModelAdmin):
-    list_display = ('id', 'name', 'category')
-    list_editable = ('name', 'category')
+    list_display = ("id", "name", "category")
+    list_editable = ("name", "category")
 
 
 admin.site.register(Category)
diff --git a/examples/cookbook/cookbook/ingredients/apps.py b/examples/cookbook/cookbook/ingredients/apps.py
index 21b4b08..3ad0143 100644
--- a/examples/cookbook/cookbook/ingredients/apps.py
+++ b/examples/cookbook/cookbook/ingredients/apps.py
@@ -2,6 +2,6 @@ from django.apps import AppConfig
 
 
 class IngredientsConfig(AppConfig):
-    name = 'cookbook.ingredients'
-    label = 'ingredients'
-    verbose_name = 'Ingredients'
+    name = "cookbook.ingredients"
+    label = "ingredients"
+    verbose_name = "Ingredients"
diff --git a/examples/cookbook/cookbook/ingredients/models.py b/examples/cookbook/cookbook/ingredients/models.py
index 2f0eba3..6426dab 100644
--- a/examples/cookbook/cookbook/ingredients/models.py
+++ b/examples/cookbook/cookbook/ingredients/models.py
@@ -11,7 +11,7 @@ class Category(models.Model):
 class Ingredient(models.Model):
     name = models.CharField(max_length=100)
     notes = models.TextField(null=True, blank=True)
-    category = models.ForeignKey(Category, related_name='ingredients')
+    category = models.ForeignKey(Category, related_name="ingredients")
 
     def __str__(self):
         return self.name
diff --git a/examples/cookbook/cookbook/ingredients/schema.py b/examples/cookbook/cookbook/ingredients/schema.py
index 5ad92e8..5e5da80 100644
--- a/examples/cookbook/cookbook/ingredients/schema.py
+++ b/examples/cookbook/cookbook/ingredients/schema.py
@@ -7,24 +7,22 @@ from graphene_django.types import DjangoObjectType
 # Graphene will automatically map the Category model's fields onto the CategoryNode.
 # This is configured in the CategoryNode's Meta class (as you can see below)
 class CategoryNode(DjangoObjectType):
-
     class Meta:
         model = Category
-        interfaces = (Node, )
-        filter_fields = ['name', 'ingredients']
+        interfaces = (Node,)
+        filter_fields = ["name", "ingredients"]
 
 
 class IngredientNode(DjangoObjectType):
-
     class Meta:
         model = Ingredient
         # Allow for some more advanced filtering here
-        interfaces = (Node, )
+        interfaces = (Node,)
         filter_fields = {
-            'name': ['exact', 'icontains', 'istartswith'],
-            'notes': ['exact', 'icontains'],
-            'category': ['exact'],
-            'category__name': ['exact'],
+            "name": ["exact", "icontains", "istartswith"],
+            "notes": ["exact", "icontains"],
+            "category": ["exact"],
+            "category__name": ["exact"],
         }
 
 
diff --git a/examples/cookbook/cookbook/ingredients/tests.py b/examples/cookbook/cookbook/ingredients/tests.py
index 4929020..a39b155 100644
--- a/examples/cookbook/cookbook/ingredients/tests.py
+++ b/examples/cookbook/cookbook/ingredients/tests.py
@@ -1,2 +1 @@
-
 # Create your tests here.
diff --git a/examples/cookbook/cookbook/ingredients/views.py b/examples/cookbook/cookbook/ingredients/views.py
index b8e4ee0..60f00ef 100644
--- a/examples/cookbook/cookbook/ingredients/views.py
+++ b/examples/cookbook/cookbook/ingredients/views.py
@@ -1,2 +1 @@
-
 # Create your views here.
diff --git a/examples/cookbook/cookbook/recipes/apps.py b/examples/cookbook/cookbook/recipes/apps.py
index 1f24f13..f1e4dde 100644
--- a/examples/cookbook/cookbook/recipes/apps.py
+++ b/examples/cookbook/cookbook/recipes/apps.py
@@ -2,6 +2,6 @@ from django.apps import AppConfig
 
 
 class RecipesConfig(AppConfig):
-    name = 'cookbook.recipes'
-    label = 'recipes'
-    verbose_name = 'Recipes'
+    name = "cookbook.recipes"
+    label = "recipes"
+    verbose_name = "Recipes"
diff --git a/examples/cookbook/cookbook/recipes/models.py b/examples/cookbook/cookbook/recipes/models.py
index ca12fac..b98664c 100644
--- a/examples/cookbook/cookbook/recipes/models.py
+++ b/examples/cookbook/cookbook/recipes/models.py
@@ -10,12 +10,15 @@ class Recipe(models.Model):
 
 
 class RecipeIngredient(models.Model):
-    recipe = models.ForeignKey(Recipe, related_name='amounts')
-    ingredient = models.ForeignKey(Ingredient, related_name='used_by')
+    recipe = models.ForeignKey(Recipe, related_name="amounts")
+    ingredient = models.ForeignKey(Ingredient, related_name="used_by")
     amount = models.FloatField()
-    unit = models.CharField(max_length=20, choices=(
-        ('unit', 'Units'),
-        ('kg', 'Kilograms'),
-        ('l', 'Litres'),
-        ('st', 'Shots'),
-    ))
+    unit = models.CharField(
+        max_length=20,
+        choices=(
+            ("unit", "Units"),
+            ("kg", "Kilograms"),
+            ("l", "Litres"),
+            ("st", "Shots"),
+        ),
+    )
diff --git a/examples/cookbook/cookbook/recipes/schema.py b/examples/cookbook/cookbook/recipes/schema.py
index 8018322..fbbedd8 100644
--- a/examples/cookbook/cookbook/recipes/schema.py
+++ b/examples/cookbook/cookbook/recipes/schema.py
@@ -3,24 +3,23 @@ from graphene import Node
 from graphene_django.filter import DjangoFilterConnectionField
 from graphene_django.types import DjangoObjectType
 
-class RecipeNode(DjangoObjectType):
 
+class RecipeNode(DjangoObjectType):
     class Meta:
         model = Recipe
-        interfaces = (Node, )
-        filter_fields = ['title','amounts']
+        interfaces = (Node,)
+        filter_fields = ["title", "amounts"]
 
 
 class RecipeIngredientNode(DjangoObjectType):
-
     class Meta:
         model = RecipeIngredient
         # Allow for some more advanced filtering here
-        interfaces = (Node, )
+        interfaces = (Node,)
         filter_fields = {
-            'ingredient__name': ['exact', 'icontains', 'istartswith'],
-            'recipe': ['exact'],
-            'recipe__title': ['icontains'],
+            "ingredient__name": ["exact", "icontains", "istartswith"],
+            "recipe": ["exact"],
+            "recipe__title": ["icontains"],
         }
 
 
diff --git a/examples/cookbook/cookbook/recipes/tests.py b/examples/cookbook/cookbook/recipes/tests.py
index 4929020..a39b155 100644
--- a/examples/cookbook/cookbook/recipes/tests.py
+++ b/examples/cookbook/cookbook/recipes/tests.py
@@ -1,2 +1 @@
-
 # Create your tests here.
diff --git a/examples/cookbook/cookbook/recipes/views.py b/examples/cookbook/cookbook/recipes/views.py
index b8e4ee0..60f00ef 100644
--- a/examples/cookbook/cookbook/recipes/views.py
+++ b/examples/cookbook/cookbook/recipes/views.py
@@ -1,2 +1 @@
-
 # Create your views here.
diff --git a/examples/cookbook/cookbook/schema.py b/examples/cookbook/cookbook/schema.py
index f91d62c..bde9372 100644
--- a/examples/cookbook/cookbook/schema.py
+++ b/examples/cookbook/cookbook/schema.py
@@ -5,10 +5,12 @@ import graphene
 from graphene_django.debug import DjangoDebug
 
 
-class Query(cookbook.ingredients.schema.Query,
-            cookbook.recipes.schema.Query,
-            graphene.ObjectType):
-    debug = graphene.Field(DjangoDebug, name='_debug')
+class Query(
+    cookbook.ingredients.schema.Query,
+    cookbook.recipes.schema.Query,
+    graphene.ObjectType,
+):
+    debug = graphene.Field(DjangoDebug, name="_debug")
 
 
 schema = graphene.Schema(query=Query)
diff --git a/examples/cookbook/cookbook/settings.py b/examples/cookbook/cookbook/settings.py
index 0b3207e..ed41a65 100644
--- a/examples/cookbook/cookbook/settings.py
+++ b/examples/cookbook/cookbook/settings.py
@@ -21,7 +21,7 @@ BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 # See https://docs.djangoproject.com/en/1.9/howto/deployment/checklist/
 
 # SECURITY WARNING: keep the secret key used in production secret!
-SECRET_KEY = '_$=$%eqxk$8ss4n7mtgarw^5$8^d5+c83!vwatr@i_81myb=e4'
+SECRET_KEY = "_$=$%eqxk$8ss4n7mtgarw^5$8^d5+c83!vwatr@i_81myb=e4"
 
 # SECURITY WARNING: don't run with debug turned on in production!
 DEBUG = True
@@ -32,65 +32,62 @@ ALLOWED_HOSTS = []
 # Application definition
 
 INSTALLED_APPS = [
-    'django.contrib.admin',
-    'django.contrib.auth',
-    'django.contrib.contenttypes',
-    'django.contrib.sessions',
-    'django.contrib.messages',
-    'django.contrib.staticfiles',
-    'graphene_django',
-
-    'cookbook.ingredients.apps.IngredientsConfig',
-    'cookbook.recipes.apps.RecipesConfig',
+    "django.contrib.admin",
+    "django.contrib.auth",
+    "django.contrib.contenttypes",
+    "django.contrib.sessions",
+    "django.contrib.messages",
+    "django.contrib.staticfiles",
+    "graphene_django",
+    "cookbook.ingredients.apps.IngredientsConfig",
+    "cookbook.recipes.apps.RecipesConfig",
 ]
 
 MIDDLEWARE_CLASSES = [
-    'django.middleware.security.SecurityMiddleware',
-    'django.contrib.sessions.middleware.SessionMiddleware',
-    'django.middleware.common.CommonMiddleware',
-    'django.middleware.csrf.CsrfViewMiddleware',
-    'django.contrib.auth.middleware.AuthenticationMiddleware',
-    'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
-    'django.contrib.messages.middleware.MessageMiddleware',
-    'django.middleware.clickjacking.XFrameOptionsMiddleware',
+    "django.middleware.security.SecurityMiddleware",
+    "django.contrib.sessions.middleware.SessionMiddleware",
+    "django.middleware.common.CommonMiddleware",
+    "django.middleware.csrf.CsrfViewMiddleware",
+    "django.contrib.auth.middleware.AuthenticationMiddleware",
+    "django.contrib.auth.middleware.SessionAuthenticationMiddleware",
+    "django.contrib.messages.middleware.MessageMiddleware",
+    "django.middleware.clickjacking.XFrameOptionsMiddleware",
 ]
 
 GRAPHENE = {
-    'SCHEMA': 'cookbook.schema.schema',
-    'SCHEMA_INDENT': 2,
-    'MIDDLEWARE': (
-        'graphene_django.debug.DjangoDebugMiddleware',
-    )
+    "SCHEMA": "cookbook.schema.schema",
+    "SCHEMA_INDENT": 2,
+    "MIDDLEWARE": ("graphene_django.debug.DjangoDebugMiddleware",),
 }
 
-ROOT_URLCONF = 'cookbook.urls'
+ROOT_URLCONF = "cookbook.urls"
 
 TEMPLATES = [
     {
-        'BACKEND': 'django.template.backends.django.DjangoTemplates',
-        'DIRS': [],
-        'APP_DIRS': True,
-        'OPTIONS': {
-            'context_processors': [
-                'django.template.context_processors.debug',
-                'django.template.context_processors.request',
-                'django.contrib.auth.context_processors.auth',
-                'django.contrib.messages.context_processors.messages',
-            ],
+        "BACKEND": "django.template.backends.django.DjangoTemplates",
+        "DIRS": [],
+        "APP_DIRS": True,
+        "OPTIONS": {
+            "context_processors": [
+                "django.template.context_processors.debug",
+                "django.template.context_processors.request",
+                "django.contrib.auth.context_processors.auth",
+                "django.contrib.messages.context_processors.messages",
+            ]
         },
-    },
+    }
 ]
 
-WSGI_APPLICATION = 'cookbook.wsgi.application'
+WSGI_APPLICATION = "cookbook.wsgi.application"
 
 
 # Database
 # https://docs.djangoproject.com/en/1.9/ref/settings/#databases
 
 DATABASES = {
-    'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
+    "default": {
+        "ENGINE": "django.db.backends.sqlite3",
+        "NAME": os.path.join(BASE_DIR, "db.sqlite3"),
     }
 }
 
@@ -100,26 +97,20 @@ DATABASES = {
 
 AUTH_PASSWORD_VALIDATORS = [
     {
-        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
+        "NAME": "django.contrib.auth.password_validation.UserAttributeSimilarityValidator"
     },
+    {"NAME": "django.contrib.auth.password_validation.MinimumLengthValidator"},
+    {"NAME": "django.contrib.auth.password_validation.CommonPasswordValidator"},
+    {"NAME": "django.contrib.auth.password_validation.NumericPasswordValidator"},
 ]
 
 
 # Internationalization
 # https://docs.djangoproject.com/en/1.9/topics/i18n/
 
-LANGUAGE_CODE = 'en-us'
+LANGUAGE_CODE = "en-us"
 
-TIME_ZONE = 'UTC'
+TIME_ZONE = "UTC"
 
 USE_I18N = True
 
@@ -131,4 +122,4 @@ USE_TZ = True
 # Static files (CSS, JavaScript, Images)
 # https://docs.djangoproject.com/en/1.9/howto/static-files/
 
-STATIC_URL = '/static/'
+STATIC_URL = "/static/"
diff --git a/examples/cookbook/cookbook/urls.py b/examples/cookbook/cookbook/urls.py
index 4bf6003..6f8a302 100644
--- a/examples/cookbook/cookbook/urls.py
+++ b/examples/cookbook/cookbook/urls.py
@@ -5,6 +5,6 @@ from graphene_django.views import GraphQLView
 
 
 urlpatterns = [
-    url(r'^admin/', admin.site.urls),
-    url(r'^graphql$', GraphQLView.as_view(graphiql=True)),
+    url(r"^admin/", admin.site.urls),
+    url(r"^graphql$", GraphQLView.as_view(graphiql=True)),
 ]
diff --git a/examples/starwars/data.py b/examples/starwars/data.py
index 9b52006..6bdbf57 100644
--- a/examples/starwars/data.py
+++ b/examples/starwars/data.py
@@ -2,97 +2,50 @@ from .models import Character, Faction, Ship
 
 
 def initialize():
-    human = Character(
-        name='Human'
-    )
+    human = Character(name="Human")
     human.save()
 
-    droid = Character(
-        name='Droid'
-    )
+    droid = Character(name="Droid")
     droid.save()
 
-    rebels = Faction(
-        id='1',
-        name='Alliance to Restore the Republic',
-        hero=human
-    )
+    rebels = Faction(id="1", name="Alliance to Restore the Republic", hero=human)
     rebels.save()
 
-    empire = Faction(
-        id='2',
-        name='Galactic Empire',
-        hero=droid
-    )
+    empire = Faction(id="2", name="Galactic Empire", hero=droid)
     empire.save()
 
-    xwing = Ship(
-        id='1',
-        name='X-Wing',
-        faction=rebels,
-    )
+    xwing = Ship(id="1", name="X-Wing", faction=rebels)
     xwing.save()
 
     human.ship = xwing
     human.save()
 
-    ywing = Ship(
-        id='2',
-        name='Y-Wing',
-        faction=rebels,
-    )
+    ywing = Ship(id="2", name="Y-Wing", faction=rebels)
     ywing.save()
 
-    awing = Ship(
-        id='3',
-        name='A-Wing',
-        faction=rebels,
-    )
+    awing = Ship(id="3", name="A-Wing", faction=rebels)
     awing.save()
 
     # Yeah, technically it's Corellian. But it flew in the service of the rebels,
     # so for the purposes of this demo it's a rebel ship.
-    falcon = Ship(
-        id='4',
-        name='Millenium Falcon',
-        faction=rebels,
-    )
+    falcon = Ship(id="4", name="Millenium Falcon", faction=rebels)
     falcon.save()
 
-    homeOne = Ship(
-        id='5',
-        name='Home One',
-        faction=rebels,
-    )
+    homeOne = Ship(id="5", name="Home One", faction=rebels)
     homeOne.save()
 
-    tieFighter = Ship(
-        id='6',
-        name='TIE Fighter',
-        faction=empire,
-    )
+    tieFighter = Ship(id="6", name="TIE Fighter", faction=empire)
     tieFighter.save()
 
-    tieInterceptor = Ship(
-        id='7',
-        name='TIE Interceptor',
-        faction=empire,
-    )
+    tieInterceptor = Ship(id="7", name="TIE Interceptor", faction=empire)
     tieInterceptor.save()
 
-    executor = Ship(
-        id='8',
-        name='Executor',
-        faction=empire,
-    )
+    executor = Ship(id="8", name="Executor", faction=empire)
     executor.save()
 
 
 def create_ship(ship_name, faction_id):
-    new_ship = Ship(
-        name=ship_name,
-        faction_id=faction_id
-    )
+    new_ship = Ship(name=ship_name, faction_id=faction_id)
     new_ship.save()
     return new_ship
 
diff --git a/examples/starwars/models.py b/examples/starwars/models.py
index 45741da..03e06a2 100644
--- a/examples/starwars/models.py
+++ b/examples/starwars/models.py
@@ -5,7 +5,13 @@ from django.db import models
 
 class Character(models.Model):
     name = models.CharField(max_length=50)
-    ship = models.ForeignKey('Ship', on_delete=models.CASCADE, blank=True, null=True, related_name='characters')
+    ship = models.ForeignKey(
+        "Ship",
+        on_delete=models.CASCADE,
+        blank=True,
+        null=True,
+        related_name="characters",
+    )
 
     def __str__(self):
         return self.name
@@ -21,7 +27,7 @@ class Faction(models.Model):
 
 class Ship(models.Model):
     name = models.CharField(max_length=50)
-    faction = models.ForeignKey(Faction, on_delete=models.CASCADE, related_name='ships')
+    faction = models.ForeignKey(Faction, on_delete=models.CASCADE, related_name="ships")
 
     def __str__(self):
         return self.name
diff --git a/examples/starwars/schema.py b/examples/starwars/schema.py
index 492918e..fb22840 100644
--- a/examples/starwars/schema.py
+++ b/examples/starwars/schema.py
@@ -2,18 +2,16 @@ import graphene
 from graphene import Schema, relay, resolve_only_args
 from graphene_django import DjangoConnectionField, DjangoObjectType
 
-from .data import (create_ship, get_empire, get_faction, get_rebels, get_ship,
-                   get_ships)
+from .data import create_ship, get_empire, get_faction, get_rebels, get_ship, get_ships
 from .models import Character as CharacterModel
 from .models import Faction as FactionModel
 from .models import Ship as ShipModel
 
 
 class Ship(DjangoObjectType):
-
     class Meta:
         model = ShipModel
-        interfaces = (relay.Node, )
+        interfaces = (relay.Node,)
 
     @classmethod
     def get_node(cls, info, id):
@@ -22,16 +20,14 @@ class Ship(DjangoObjectType):
 
 
 class Character(DjangoObjectType):
-
     class Meta:
         model = CharacterModel
 
 
 class Faction(DjangoObjectType):
-
     class Meta:
         model = FactionModel
-        interfaces = (relay.Node, )
+        interfaces = (relay.Node,)
 
     @classmethod
     def get_node(cls, info, id):
@@ -39,7 +35,6 @@ class Faction(DjangoObjectType):
 
 
 class IntroduceShip(relay.ClientIDMutation):
-
     class Input:
         ship_name = graphene.String(required=True)
         faction_id = graphene.String(required=True)
@@ -48,7 +43,9 @@ class IntroduceShip(relay.ClientIDMutation):
     faction = graphene.Field(Faction)
 
     @classmethod
-    def mutate_and_get_payload(cls, root, info, ship_name, faction_id, client_mutation_id=None):
+    def mutate_and_get_payload(
+        cls, root, info, ship_name, faction_id, client_mutation_id=None
+    ):
         ship = create_ship(ship_name, faction_id)
         faction = get_faction(faction_id)
         return IntroduceShip(ship=ship, faction=faction)
@@ -58,7 +55,7 @@ class Query(graphene.ObjectType):
     rebels = graphene.Field(Faction)
     empire = graphene.Field(Faction)
     node = relay.Node.Field()
-    ships = DjangoConnectionField(Ship, description='All the ships.')
+    ships = DjangoConnectionField(Ship, description="All the ships.")
 
     @resolve_only_args
     def resolve_ships(self):
diff --git a/examples/starwars/tests/test_connections.py b/examples/starwars/tests/test_connections.py
index d266df3..425dce5 100644
--- a/examples/starwars/tests/test_connections.py
+++ b/examples/starwars/tests/test_connections.py
@@ -8,7 +8,7 @@ pytestmark = pytest.mark.django_db
 
 def test_correct_fetch_first_ship_rebels():
     initialize()
-    query = '''
+    query = """
     query RebelsShipsQuery {
       rebels {
         name,
@@ -24,22 +24,12 @@ def test_correct_fetch_first_ship_rebels():
         }
       }
     }
-    '''
+    """
     expected = {
-        'rebels': {
-            'name': 'Alliance to Restore the Republic',
-            'hero': {
-                'name': 'Human'
-            },
-            'ships': {
-                'edges': [
-                    {
-                        'node': {
-                            'name': 'X-Wing'
-                        }
-                    }
-                ]
-            }
+        "rebels": {
+            "name": "Alliance to Restore the Republic",
+            "hero": {"name": "Human"},
+            "ships": {"edges": [{"node": {"name": "X-Wing"}}]},
         }
     }
     result = schema.execute(query)
@@ -49,7 +39,7 @@ def test_correct_fetch_first_ship_rebels():
 
 def test_correct_list_characters():
     initialize()
-    query = '''
+    query = """
     query RebelsShipsQuery {
       node(id: "U2hpcDox") {
         ... on Ship {
@@ -60,15 +50,8 @@ def test_correct_list_characters():
         }
       }
     }
-    '''
-    expected = {
-        'node': {
-            'name': 'X-Wing',
-            'characters': [{
-                'name': 'Human'
-            }],
-        }
-    }
+    """
+    expected = {"node": {"name": "X-Wing", "characters": [{"name": "Human"}]}}
     result = schema.execute(query)
     assert not result.errors
     assert result.data == expected
diff --git a/examples/starwars/tests/test_mutation.py b/examples/starwars/tests/test_mutation.py
index aa312ff..e24bf8a 100644
--- a/examples/starwars/tests/test_mutation.py
+++ b/examples/starwars/tests/test_mutation.py
@@ -9,7 +9,7 @@ pytestmark = pytest.mark.django_db
 def test_mutations():
     initialize()
 
-    query = '''
+    query = """
     mutation MyMutation {
       introduceShip(input:{clientMutationId:"abc", shipName: "Peter", factionId: "1"}) {
         ship {
@@ -29,49 +29,23 @@ def test_mutations():
         }
       }
     }
-    '''
+    """
     expected = {
-        'introduceShip': {
-            'ship': {
-                'id': 'U2hpcDo5',
-                'name': 'Peter'
-            },
-            'faction': {
-                'name': 'Alliance to Restore the Republic',
-                'ships': {
-                    'edges': [{
-                        'node': {
-                            'id': 'U2hpcDox',
-                            'name': 'X-Wing'
-                        }
-                    }, {
-                        'node': {
-                            'id': 'U2hpcDoy',
-                            'name': 'Y-Wing'
-                        }
-                    }, {
-                        'node': {
-                            'id': 'U2hpcDoz',
-                            'name': 'A-Wing'
-                        }
-                    }, {
-                        'node': {
-                            'id': 'U2hpcDo0',
-                            'name': 'Millenium Falcon'
-                        }
-                    }, {
-                        'node': {
-                            'id': 'U2hpcDo1',
-                            'name': 'Home One'
-                        }
-                    }, {
-                        'node': {
-                            'id': 'U2hpcDo5',
-                            'name': 'Peter'
-                        }
-                    }]
+        "introduceShip": {
+            "ship": {"id": "U2hpcDo5", "name": "Peter"},
+            "faction": {
+                "name": "Alliance to Restore the Republic",
+                "ships": {
+                    "edges": [
+                        {"node": {"id": "U2hpcDox", "name": "X-Wing"}},
+                        {"node": {"id": "U2hpcDoy", "name": "Y-Wing"}},
+                        {"node": {"id": "U2hpcDoz", "name": "A-Wing"}},
+                        {"node": {"id": "U2hpcDo0", "name": "Millenium Falcon"}},
+                        {"node": {"id": "U2hpcDo1", "name": "Home One"}},
+                        {"node": {"id": "U2hpcDo5", "name": "Peter"}},
+                    ]
                 },
-            }
+            },
         }
     }
     result = schema.execute(query)
diff --git a/examples/starwars/tests/test_objectidentification.py b/examples/starwars/tests/test_objectidentification.py
index fad1958..6e04a7b 100644
--- a/examples/starwars/tests/test_objectidentification.py
+++ b/examples/starwars/tests/test_objectidentification.py
@@ -8,19 +8,16 @@ pytestmark = pytest.mark.django_db
 
 def test_correctly_fetches_id_name_rebels():
     initialize()
-    query = '''
+    query = """
       query RebelsQuery {
         rebels {
           id
           name
         }
       }
-    '''
+    """
     expected = {
-        'rebels': {
-            'id': 'RmFjdGlvbjox',
-            'name': 'Alliance to Restore the Republic'
-        }
+        "rebels": {"id": "RmFjdGlvbjox", "name": "Alliance to Restore the Republic"}
     }
     result = schema.execute(query)
     assert not result.errors
@@ -29,7 +26,7 @@ def test_correctly_fetches_id_name_rebels():
 
 def test_correctly_refetches_rebels():
     initialize()
-    query = '''
+    query = """
       query RebelsRefetchQuery {
         node(id: "RmFjdGlvbjox") {
           id
@@ -38,12 +35,9 @@ def test_correctly_refetches_rebels():
           }
         }
       }
-    '''
+    """
     expected = {
-        'node': {
-            'id': 'RmFjdGlvbjox',
-            'name': 'Alliance to Restore the Republic'
-        }
+        "node": {"id": "RmFjdGlvbjox", "name": "Alliance to Restore the Republic"}
     }
     result = schema.execute(query)
     assert not result.errors
@@ -52,20 +46,15 @@ def test_correctly_refetches_rebels():
 
 def test_correctly_fetches_id_name_empire():
     initialize()
-    query = '''
+    query = """
       query EmpireQuery {
         empire {
           id
           name
         }
       }
-    '''
-    expected = {
-        'empire': {
-            'id': 'RmFjdGlvbjoy',
-            'name': 'Galactic Empire'
-        }
-    }
+    """
+    expected = {"empire": {"id": "RmFjdGlvbjoy", "name": "Galactic Empire"}}
     result = schema.execute(query)
     assert not result.errors
     assert result.data == expected
@@ -73,7 +62,7 @@ def test_correctly_fetches_id_name_empire():
 
 def test_correctly_refetches_empire():
     initialize()
-    query = '''
+    query = """
       query EmpireRefetchQuery {
         node(id: "RmFjdGlvbjoy") {
           id
@@ -82,13 +71,8 @@ def test_correctly_refetches_empire():
           }
         }
       }
-    '''
-    expected = {
-        'node': {
-            'id': 'RmFjdGlvbjoy',
-            'name': 'Galactic Empire'
-        }
-    }
+    """
+    expected = {"node": {"id": "RmFjdGlvbjoy", "name": "Galactic Empire"}}
     result = schema.execute(query)
     assert not result.errors
     assert result.data == expected
@@ -96,7 +80,7 @@ def test_correctly_refetches_empire():
 
 def test_correctly_refetches_xwing():
     initialize()
-    query = '''
+    query = """
       query XWingRefetchQuery {
         node(id: "U2hpcDox") {
           id
@@ -105,13 +89,8 @@ def test_correctly_refetches_xwing():
           }
         }
       }
-    '''
-    expected = {
-        'node': {
-            'id': 'U2hpcDox',
-            'name': 'X-Wing'
-        }
-    }
+    """
+    expected = {"node": {"id": "U2hpcDox", "name": "X-Wing"}}
     result = schema.execute(query)
     assert not result.errors
     assert result.data == expected
diff --git a/graphene_django/converter.py b/graphene_django/converter.py
index 158355a..1bb16f4 100644
--- a/graphene_django/converter.py
+++ b/graphene_django/converter.py
@@ -177,7 +177,11 @@ def convert_field_to_list_or_connection(field, registry=None):
         if not _type:
             return
 
-        description = field.help_text if isinstance(field, models.ManyToManyField) else field.field.help_text
+        description = (
+            field.help_text
+            if isinstance(field, models.ManyToManyField)
+            else field.field.help_text
+        )
 
         # If there is a connection, we should transform the field
         # into a DjangoConnectionField
diff --git a/graphene_django/filter/fields.py b/graphene_django/filter/fields.py
index 7c85e9a..62f4b1a 100644
--- a/graphene_django/filter/fields.py
+++ b/graphene_django/filter/fields.py
@@ -41,10 +41,9 @@ class DjangoFilterConnectionField(DjangoConnectionField):
                 meta.update(self._extra_filter_meta)
 
             filterset_class = self._provided_filterset_class or (
-                self.node_type._meta.filterset_class)
-            self._filterset_class = get_filterset_class(
-                filterset_class, **meta
+                self.node_type._meta.filterset_class
             )
+            self._filterset_class = get_filterset_class(filterset_class, **meta)
 
         return self._filterset_class
 
diff --git a/graphene_django/filter/tests/test_fields.py b/graphene_django/filter/tests/test_fields.py
index eb6581b..4d8d597 100644
--- a/graphene_django/filter/tests/test_fields.py
+++ b/graphene_django/filter/tests/test_fields.py
@@ -229,6 +229,7 @@ def test_filter_filterset_information_on_meta_related():
 
 def test_filter_filterset_class_filter_fields_exception():
     with pytest.raises(Exception):
+
         class ReporterFilter(FilterSet):
             class Meta:
                 model = Reporter
diff --git a/graphene_django/rest_framework/tests/test_mutation.py b/graphene_django/rest_framework/tests/test_mutation.py
index a0c861d..9621ee3 100644
--- a/graphene_django/rest_framework/tests/test_mutation.py
+++ b/graphene_django/rest_framework/tests/test_mutation.py
@@ -104,7 +104,9 @@ def test_write_only_field():
     )
 
     assert hasattr(result, "cool_name")
-    assert not hasattr(result, "password"), "'password' is write_only field and shouldn't be visible"
+    assert not hasattr(
+        result, "password"
+    ), "'password' is write_only field and shouldn't be visible"
 
 
 @mark.django_db
@@ -124,7 +126,9 @@ def test_write_only_field_using_extra_kwargs():
     )
 
     assert hasattr(result, "cool_name")
-    assert not hasattr(result, "password"), "'password' is write_only field and shouldn't be visible"
+    assert not hasattr(
+        result, "password"
+    ), "'password' is write_only field and shouldn't be visible"
 
 
 def test_nested_model():
diff --git a/graphene_django/tests/test_query.py b/graphene_django/tests/test_query.py
index 9ef217e..484a225 100644
--- a/graphene_django/tests/test_query.py
+++ b/graphene_django/tests/test_query.py
@@ -1015,13 +1015,13 @@ def test_proxy_model_support():
             "edges": [
                 {"node": {"id": to_global_id("CNNReporterType", cnn_reporter.id)}}
             ]
-        }
+        },
     }
 
     result = schema.execute(query)
     assert not result.errors
     assert result.data == expected
-    
+
 
 def test_should_resolve_get_queryset_connectionfields():
     reporter_1 = Reporter.objects.create(
diff --git a/graphene_django/types.py b/graphene_django/types.py
index ded8a15..a1e17b3 100644
--- a/graphene_django/types.py
+++ b/graphene_django/types.py
@@ -82,10 +82,12 @@ class DjangoObjectType(ObjectType):
             raise Exception("Can't set both filter_fields and filterset_class")
 
         if not DJANGO_FILTER_INSTALLED and (filter_fields or filterset_class):
-            raise Exception((
-                "Can only set filter_fields or filterset_class if "
-                "Django-Filter is installed"
-            ))
+            raise Exception(
+                (
+                    "Can only set filter_fields or filterset_class if "
+                    "Django-Filter is installed"
+                )
+            )
 
         django_fields = yank_fields_from_attrs(
             construct_fields(model, registry, only_fields, exclude_fields), _as=Field
diff --git a/tox.ini b/tox.ini
index 8e21c74..58f283a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,31 +1,39 @@
 [tox]
-envlist = py{2.7,3.4,3.5,3.6,3.7,pypy,pypy3}-django{1.10,1.11,2.0,2.1,2.2,master},lint
+envlist =
+    py{27,35,36,37}-django{111,20,21,22,master},
+    black,flake8
+
+[travis:env]
+DJANGO =
+    1.11: django111
+    2.0: django20
+    2.1: django21
+    2.2: django22
+    master: djangomaster
 
 [testenv]
 passenv = *
 usedevelop = True
-setenv = 
+setenv =
     DJANGO_SETTINGS_MODULE=django_test_settings
-basepython =
-    py2.7: python2.7
-    py3.4: python3.4
-    py3.5: python3.5
-    py3.6: python3.6
-    py3.7: python3.7
-    pypypy: pypy
-    pypypy3: pypy3
 deps =
     -e.[test]
     psycopg2
-    django1.10: Django>=1.10,<1.11
-    django1.11: Django>=1.11,<1.12
-    django2.0: Django>=2.0
-    django2.1: Django>=2.1
+    django111: Django>=1.11,<2.0
+    django20: Django>=2.0,<2.1
+    django21: Django>=2.1,<2.2
+    django22: Django>=2.2,<3.0
     djangomaster: https://github.com/django/django/archive/master.zip
 commands = {posargs:py.test --cov=graphene_django graphene_django examples}
 
-[testenv:lint]
-basepython = python
-deps =
-    prospector
-commands = prospector graphene_django -0
+[testenv:black]
+basepython = python3.7
+deps = black
+commands  =
+    black --exclude "/migrations/" graphene_django examples --check
+
+[testenv:flake8]
+basepython = python3.7
+deps = flake8
+commands =
+    flake8 graphene_django examples