diff --git a/.travis.yml b/.travis.yml
index 6adedbb..69392d6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -39,20 +39,27 @@ env:
   - PG=9.6 DJANGO=2.1
   - PG=10 DJANGO=2.1
   - PG=11 DJANGO=2.1
+  - PG=12 DJANGO=2.1
   - PG=9.6 DJANGO=2.2
   - PG=10 DJANGO=2.2
   - PG=11 DJANGO=2.2
+  - PG=12 DJANGO=2.2
   - PG=9.6 DJANGO=3.0
   - PG=10 DJANGO=3.0
   - PG=11 DJANGO=3.0
+  - PG=12 DJANGO=3.0
 
 before_install:
   # Use default PostgreSQL 11 port
   - sudo sed -i 's/port = 5433/port = 5432/' /etc/postgresql/11/main/postgresql.conf
   - sudo cp /etc/postgresql/{10,11}/main/pg_hba.conf
 
+  - sudo sed -i 's/port = 5434/port = 5432/' /etc/postgresql/12/main/postgresql.conf
+  - sudo cp /etc/postgresql/{10,12}/main/pg_hba.conf
+
   # Start PostgreSQL version we need
-  - sudo systemctl stop postgresql && sudo systemctl start postgresql@$PG-main
+  - sudo systemctl stop postgresql
+  - sudo systemctl start postgresql@$PG-main
 
   # ClickHouse sources
   - sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv E0C56BD4
diff --git a/src/django_clickhouse/clickhouse_models.py b/src/django_clickhouse/clickhouse_models.py
index eaa47a1..343df18 100644
--- a/src/django_clickhouse/clickhouse_models.py
+++ b/src/django_clickhouse/clickhouse_models.py
@@ -94,12 +94,11 @@ class ClickHouseModel(with_metaclass(ClickHouseModelMeta, InfiModel)):
         return namedtuple("%sTuple" % cls.__name__, field_names, defaults=default_values)
 
     @classmethod
-    def objects_in(cls, database):  # type: (Database) -> QuerySet
+    def objects_in(cls, database: Database)-> QuerySet:
         return QuerySet(cls, database)
 
     @classmethod
-    def get_database_alias(cls, for_write=False):
-        # type: (bool) -> str
+    def get_database_alias(cls, for_write: bool = False) -> str:
         """
         Gets database alias for read or write purposes
         :param for_write: Boolean flag if database is neede for read or for write
@@ -112,8 +111,7 @@ class ClickHouseModel(with_metaclass(ClickHouseModelMeta, InfiModel)):
             return db_router.db_for_read(cls)
 
     @classmethod
-    def get_database(cls, for_write=False):
-        # type: (bool) -> Database
+    def get_database(cls, for_write: bool = False) -> Database:
         """
         Gets database alias for read or write purposes
         :param for_write: Boolean flag if database is neede for read or for write
@@ -123,8 +121,8 @@ class ClickHouseModel(with_metaclass(ClickHouseModelMeta, InfiModel)):
         return connections[db_alias]
 
     @classmethod
-    def get_django_model_serializer(cls, writable=False, defaults=None):
-        # type: (bool, Optional[dict]) -> Django2ClickHouseModelSerializer
+    def get_django_model_serializer(cls, writable: bool= False, defaults: Optional[dict] = None
+                                    ) -> Django2ClickHouseModelSerializer:
         serializer_cls = lazy_class_import(cls.django_model_serializer)
         return serializer_cls(cls, writable=writable, defaults=defaults)
 
@@ -171,7 +169,7 @@ class ClickHouseModel(with_metaclass(ClickHouseModelMeta, InfiModel)):
         return True
 
     @classmethod
-    def get_sync_query_set(cls, using, pk_set):  # type: (str, Set[Any]) -> DjangoQuerySet
+    def get_sync_query_set(cls, using: str, pk_set: Set[Any]) -> DjangoQuerySet:
         """
         Forms django queryset to fetch for sync
         :param using: Database to fetch from
@@ -181,7 +179,7 @@ class ClickHouseModel(with_metaclass(ClickHouseModelMeta, InfiModel)):
         return cls.django_model.objects.filter(pk__in=pk_set).using(using)
 
     @classmethod
-    def get_sync_objects(cls, operations):  # type: (List[Tuple[str, str]]) -> List[DjangoModel]
+    def get_sync_objects(cls, operations: List[Tuple[str, str]]) -> List[DjangoModel]:
         """
         Returns objects from main database to sync
         :param operations: A list of operations to perform
@@ -203,7 +201,7 @@ class ClickHouseModel(with_metaclass(ClickHouseModelMeta, InfiModel)):
         return list(chain(*objs))
 
     @classmethod
-    def get_insert_batch(cls, import_objects):  # type: (Iterable[DjangoModel]) -> List[ClickHouseModel]
+    def get_insert_batch(cls, import_objects: Iterable[DjangoModel]) -> List['ClickHouseModel']:
         """
         Formats django model objects to batch of ClickHouse objects
         :param import_objects: DjangoModel objects to import
@@ -267,7 +265,7 @@ class ClickHouseModel(with_metaclass(ClickHouseModelMeta, InfiModel)):
             raise ex
 
     @classmethod
-    def need_sync(cls):  # type: () -> bool
+    def need_sync(cls) -> bool:
         """
         Checks if this model needs synchronization: sync is enabled and delay has passed
         :return: Boolean
diff --git a/src/django_clickhouse/configuration.py b/src/django_clickhouse/configuration.py
index 3467eb3..2c44872 100644
--- a/src/django_clickhouse/configuration.py
+++ b/src/django_clickhouse/configuration.py
@@ -28,7 +28,7 @@ DEFAULTS = {
 
 
 class Config:
-    def __getattr__(self, item):  # type: (str) -> Any
+    def __getattr__(self, item: str) -> Any:
         if item not in DEFAULTS:
             raise AttributeError('Unknown config parameter `%s`' % item)
 
diff --git a/src/django_clickhouse/database.py b/src/django_clickhouse/database.py
index 6abc516..516d533 100644
--- a/src/django_clickhouse/database.py
+++ b/src/django_clickhouse/database.py
@@ -35,8 +35,8 @@ class Database(InfiDatabase):
     def _get_applied_migrations(self, migrations_package_name):
         raise NotImplementedError("This method is not supported by django_clickhouse.")
 
-    def select_tuples(self, query, model_class, settings=None):
-        # type: (str, Type['ClickHouseModel'], Optional[dict], Optional[dict]) -> Generator[tuple]
+    def select_tuples(self, query: str, model_class: Type['ClickHouseModel'], settings: Optional[dict] = None
+                      ) -> Iterable[tuple]:
         """
         This method selects model_class namedtuples, instead of class instances.
         Less memory consumption, greater speed
@@ -67,11 +67,11 @@ class Database(InfiDatabase):
 
                 yield item
 
-    def insert_tuples(self, model_class, model_tuples, batch_size=None, formatted=False):
-        # type: (Type['ClickHouseModel'], Iterable[tuple], Optional[int], bool) -> None
+    def insert_tuples(self, model_class: Type['ClickHouseModel'], model_tuples: Iterable[tuple],
+                      batch_size: Optional[int] = None, formatted: bool = False) -> None:
         """
         Inserts model_class namedtuples
-        :param model_class: Clickhouse model, namedtuples are made from
+        :param model_class: ClickHouse model, namedtuples are made from
         :param model_tuples: An iterable of tuples to insert
         :param batch_size: Size of batch
         :param formatted: If flag is set, tuples are expected to be ready to insert without calling field.to_db_string
diff --git a/src/django_clickhouse/engines.py b/src/django_clickhouse/engines.py
index 46cf26b..55e1647 100644
--- a/src/django_clickhouse/engines.py
+++ b/src/django_clickhouse/engines.py
@@ -2,7 +2,7 @@
 This file contains wrappers for infi.clckhouse_orm engines to use in django-clickhouse
 """
 import datetime
-from typing import List, Type, Union, Iterable, Generator
+from typing import List, Type, Union, Iterable, Generator, Optional
 
 from django.db.models import Model as DjangoModel
 from infi.clickhouse_orm import engines as infi_engines
@@ -14,8 +14,7 @@ from .utils import format_datetime
 
 
 class InsertOnlyEngineMixin:
-    def get_insert_batch(self, model_cls, objects):
-        # type: (Type['ClickHouseModel'], List[DjangoModel]) -> Generator[tuple]
+    def get_insert_batch(self, model_cls: Type['ClickHouseModel'], objects: List[DjangoModel]) -> Iterable[tuple]:
         """
         Gets a list of model_cls instances to insert into database
         :param model_cls: ClickHouseModel subclass to import
@@ -69,8 +68,8 @@ class CollapsingMergeTree(InsertOnlyEngineMixin, infi_engines.CollapsingMergeTre
                              max_date=max_date, object_pks=','.join(object_pks))
         return connections[db_alias].select_tuples(query, model_cls)
 
-    def get_final_versions(self, model_cls, objects, date_col=None):
-        # type: (Type['ClickHouseModel'], Iterable[DjangoModel], str) -> Generator[tuple]
+    def get_final_versions(self, model_cls: Type['ClickHouseModel'], objects: Iterable[DjangoModel],
+                           date_col: Optional[str] = None) -> Iterable[tuple]:
         """
         Get objects, that are currently stored in ClickHouse.
         Depending on the partition key this can be different for different models.
@@ -82,7 +81,7 @@ class CollapsingMergeTree(InsertOnlyEngineMixin, infi_engines.CollapsingMergeTre
         :return: A generator of named tuples, representing previous state
         """
 
-        def _dt_to_str(dt):  # type: (Union[datetime.date, datetime.datetime]) -> str
+        def _dt_to_str(dt: Union[datetime.date, datetime.datetime]) -> str:
             if isinstance(dt, datetime.datetime):
                 return format_datetime(dt, 0, db_alias=db_alias)
             elif isinstance(dt, datetime.date):
@@ -123,8 +122,7 @@ class CollapsingMergeTree(InsertOnlyEngineMixin, infi_engines.CollapsingMergeTre
         else:
             return self._get_final_versions_by_final(*params)
 
-    def get_insert_batch(self, model_cls, objects):
-        # type: (Type['ClickHouseModel'], List[DjangoModel]) -> Generator[tuple]
+    def get_insert_batch(self, model_cls: Type['ClickHouseModel'], objects: List[DjangoModel]) -> Iterable[tuple]:
         """
         Gets a list of model_cls instances to insert into database
         :param model_cls: ClickHouseModel subclass to import
diff --git a/src/django_clickhouse/migrations.py b/src/django_clickhouse/migrations.py
index 2f1d9e7..62ccd18 100644
--- a/src/django_clickhouse/migrations.py
+++ b/src/django_clickhouse/migrations.py
@@ -23,7 +23,7 @@ class Migration:
     """
     operations = []
 
-    def apply(self, db_alias, database=None):  # type: (str, Optional[Database]) -> None
+    def apply(self, db_alias: str, database: Optional[Database] = None) -> None:
         """
         Applies migration to given database
         :param db_alias: Database alias to apply migration to
@@ -41,8 +41,7 @@ class Migration:
                 op.apply(database)
 
 
-def migrate_app(app_label, db_alias, up_to=9999, database=None):
-    # type: (str, str, int, Optional[Database]) -> None
+def migrate_app(app_label: str, db_alias: str, up_to: int = 9999, database: Optional[Database] = None) -> None:
     """
     Migrates given django app
     :param app_label: App label to migrate
@@ -110,7 +109,7 @@ class MigrationHistory(ClickHouseModel):
     engine = MergeTree('applied', ('db_alias', 'package_name', 'module_name'))
 
     @classmethod
-    def set_migration_applied(cls, db_alias, migrations_package, name):  # type: (str, str, str) -> None
+    def set_migration_applied(cls, db_alias: str, migrations_package: str, name: str) -> None:
         """
         Sets migration apply status
         :param db_alias: Database alias migration is applied to
@@ -126,7 +125,7 @@ class MigrationHistory(ClickHouseModel):
                            applied=datetime.date.today())
 
     @classmethod
-    def get_applied_migrations(cls, db_alias, migrations_package):  # type: (str, str) -> Set[str]
+    def get_applied_migrations(cls, db_alias: str, migrations_package: str) -> Set[str]:
         """
         Returns applied migrations names
         :param db_alias: Database alias, to check
diff --git a/src/django_clickhouse/models.py b/src/django_clickhouse/models.py
index 9d38206..7342719 100644
--- a/src/django_clickhouse/models.py
+++ b/src/django_clickhouse/models.py
@@ -5,7 +5,6 @@ It saves all operations to storage in order to write them to ClickHouse later.
 
 from typing import Optional, Any, Type, Set
 
-import functools
 import six
 from django.db import transaction
 from django.db.models import QuerySet as DjangoQuerySet, Model as DjangoModel, Manager as DjangoManager
@@ -147,7 +146,7 @@ class ClickHouseSyncModel(DjangoModel):
         abstract = True
 
     @classmethod
-    def get_clickhouse_storage(cls):  # type: () -> Storage
+    def get_clickhouse_storage(cls) -> Storage:
         """
         Returns Storage instance to save clickhouse sync data to
         :return:
@@ -156,8 +155,7 @@ class ClickHouseSyncModel(DjangoModel):
         return storage_cls()
 
     @classmethod
-    def register_clickhouse_sync_model(cls, model_cls):
-        # type: (Type['django_clickhouse.clickhouse_models.ClickHouseModel']) -> None
+    def register_clickhouse_sync_model(cls, model_cls: Type['ClickHouseModel']) -> None:
         """
         Registers ClickHouse model to listen to this model updates
         :param model_cls: Model class to register
@@ -169,7 +167,7 @@ class ClickHouseSyncModel(DjangoModel):
         cls._clickhouse_sync_models.add(model_cls)
 
     @classmethod
-    def get_clickhouse_sync_models(cls):  # type: () -> Set['django_clickhouse.clickhouse_models.ClickHouseModel']
+    def get_clickhouse_sync_models(cls) -> Set['ClickHouseModel']:
         """
         Returns all clickhouse models, listening to this class
         :return: A set of model classes to sync
@@ -177,8 +175,7 @@ class ClickHouseSyncModel(DjangoModel):
         return getattr(cls, '_clickhouse_sync_models', set())
 
     @classmethod
-    def register_clickhouse_operations(cls, operation, *model_pks, using=None):
-        # type: (str, *Any, Optional[str]) -> None
+    def register_clickhouse_operations(cls, operation: str, *model_pks: Any, using: Optional[str] = None) -> None:
         """
         Registers model operation in storage
         :param operation: Operation type - one of [insert, update, delete)
@@ -197,10 +194,10 @@ class ClickHouseSyncModel(DjangoModel):
             storage = cls.get_clickhouse_storage()
             transaction.on_commit(_on_commit, using=using)
 
-    def post_save(self, created, using=None):  # type: (bool, Optional[str]) -> None
+    def post_save(self, created: bool, using: Optional[str] = None) -> None:
         self.register_clickhouse_operations('insert' if created else 'update', self.pk, using=using)
 
-    def post_delete(self, using=None):  # type: (Optional[str]) -> None
+    def post_delete(self, using: Optional[str] = None) -> None:
         self.register_clickhouse_operations('delete', self.pk, using=using)
 
 
diff --git a/src/django_clickhouse/query.py b/src/django_clickhouse/query.py
index 9cccc40..c31ba91 100644
--- a/src/django_clickhouse/query.py
+++ b/src/django_clickhouse/query.py
@@ -1,4 +1,4 @@
-from typing import Optional, Iterable, List
+from typing import Optional, Iterable, List, Type
 
 from copy import copy
 from infi.clickhouse_orm.database import Database
@@ -13,22 +13,22 @@ class QuerySet(InfiQuerySet):
     Basic QuerySet to use
     """
 
-    def __init__(self, model_cls, database=None):  # type: (Type[InfiModel], Optional[Database]) -> None
+    def __init__(self, model_cls: Type[InfiModel], database: Optional[Database] = None) -> None:
         super(QuerySet, self).__init__(model_cls, database)
         self._db_alias = None
 
     @property
-    def _database(self):  # type: () -> Database
+    def _database(self) -> Database:
         # HACK for correct work of all infi.clickhouse-orm methods
         # There are no write QuerySet methods now, so I use for_write=False by default
         return self.get_database(for_write=False)
 
     @_database.setter
-    def _database(self, database):  # type: (Database) -> None
+    def _database(self, database: Database) -> None:
         # HACK for correct work of all infi.clickhouse-orm methods
         self._db = database
 
-    def get_database(self, for_write=False):  # type: (bool) -> Database
+    def get_database(self, for_write: bool = False) -> Database:
         """
         Gets database to execute query on. Looks for constructor or using() method.
         If nothing was set tries to get database from model class using router.
@@ -43,7 +43,7 @@ class QuerySet(InfiQuerySet):
 
         return self._db
 
-    def using(self, db_alias):  # type: (str) -> QuerySet
+    def using(self, db_alias: str) -> 'QuerySet':
         """
         Sets database alias to use for this query
         :param db_alias: Database alias name from CLICKHOUSE_DATABASES config option
@@ -54,7 +54,7 @@ class QuerySet(InfiQuerySet):
         qs._db = None  # Previous database should be forgotten
         return qs
 
-    def all(self):  # type: () -> QuerySet
+    def all(self) -> 'QuerySet':
         """
         Returns all items of queryset
         :return: QuerySet
@@ -70,7 +70,7 @@ class QuerySet(InfiQuerySet):
         self.get_database(for_write=True).insert([instance])
         return instance
 
-    def bulk_create(self, model_instances, batch_size=1000):  # type: (Iterable[InfiModel], int) -> List[InfiModel]
+    def bulk_create(self, model_instances: Iterable[InfiModel], batch_size: int = 1000) -> List[InfiModel]:
         self.get_database(for_write=True).insert(model_instances=model_instances, batch_size=batch_size)
         return list(model_instances)
 
diff --git a/src/django_clickhouse/routers.py b/src/django_clickhouse/routers.py
index f56de90..9fcfe54 100644
--- a/src/django_clickhouse/routers.py
+++ b/src/django_clickhouse/routers.py
@@ -1,7 +1,7 @@
 """
 This file defines router to find appropriate database
 """
-from typing import Optional
+from typing import Type
 
 import random
 import six
@@ -13,8 +13,7 @@ from .utils import lazy_class_import
 
 
 class DefaultRouter:
-    def db_for_read(self, model, **hints):
-        # type: (ClickHouseModel, **dict) -> str
+    def db_for_read(self, model: Type[ClickHouseModel], **hints) -> str:
         """
         Gets database to read from for model
         :param model: Model to decide for
@@ -23,8 +22,7 @@ class DefaultRouter:
         """
         return random.choice(model.read_db_aliases)
 
-    def db_for_write(self, model, **hints):
-        # type: (ClickHouseModel, **dict) -> str
+    def db_for_write(self, model: Type[ClickHouseModel], **hints) -> str:
         """
         Gets database to write to for model
         :param model: Model to decide for
@@ -33,8 +31,8 @@ class DefaultRouter:
         """
         return random.choice(model.write_db_aliases)
 
-    def allow_migrate(self, db_alias, app_label, operation, model=None, **hints):
-        # type: (str, str, Operation, Optional[ClickHouseModel], **dict) -> bool
+    def allow_migrate(self, db_alias: str, app_label: str, operation: Operation,
+                      model=None, **hints) -> bool:
         """
         Checks if migration can be applied to given database
         :param db_alias: Database alias to check
diff --git a/src/django_clickhouse/serializers.py b/src/django_clickhouse/serializers.py
index bfb2a76..4b3907e 100644
--- a/src/django_clickhouse/serializers.py
+++ b/src/django_clickhouse/serializers.py
@@ -1,4 +1,4 @@
-from typing import NamedTuple
+from typing import NamedTuple, Optional, Iterable, Type
 
 import pytz
 from django.db.models import Model as DjangoModel
@@ -7,7 +7,19 @@ from .utils import model_to_dict
 
 
 class Django2ClickHouseModelSerializer:
-    def __init__(self, model_cls, fields=None, exclude_fields=None, writable=False, defaults=None):
+    def __init__(self, model_cls: Type['ClickHouseModel'], fields: Optional[Iterable[str]] = None,
+                 exclude_fields: Optional[Iterable[str]] = None, writable: bool = False,
+                 defaults: Optional[dict] = None) -> None:
+        """
+        Initializes serializer
+        :param model_cls: ClickHouseModel subclass to serialize to
+        :param fields: Optional. A list of fields to add into result tuple
+        :param exclude_fields: Fields to exclude from result tuple
+        :param writable: If fields parameter is not set directly,
+          this flags determines if only writable or all fields should be taken from model_cls
+        :param defaults: A dictionary of field: value which are taken as default values for model_cls instances
+        :return: None
+        """
         self._model_cls = model_cls
         if fields is not None:
             self.serialize_fields = fields
@@ -18,7 +30,7 @@ class Django2ClickHouseModelSerializer:
         self._result_class = self._model_cls.get_tuple_class(defaults=defaults)
         self._fields = self._model_cls.fields(writable=False)
 
-    def _get_serialize_kwargs(self, obj):
+    def _get_serialize_kwargs(self, obj: DjangoModel) -> dict:
         data = model_to_dict(obj, fields=self.serialize_fields, exclude_fields=self.exclude_serialize_fields)
 
         # Remove None values, they should be initialized as defaults
@@ -29,5 +41,5 @@ class Django2ClickHouseModelSerializer:
 
         return result
 
-    def serialize(self, obj):  # type: (DjangoModel) -> NamedTuple
+    def serialize(self, obj: DjangoModel) -> NamedTuple:
         return self._result_class(**self._get_serialize_kwargs(obj))
diff --git a/src/django_clickhouse/storages.py b/src/django_clickhouse/storages.py
index 84720a4..dcdfceb 100644
--- a/src/django_clickhouse/storages.py
+++ b/src/django_clickhouse/storages.py
@@ -39,7 +39,7 @@ class Storage:
     But ClickHouse is idempotent to duplicate inserts. So we can insert one batch twice correctly.
     """
 
-    def pre_sync(self, import_key, **kwargs):  # type: (str, **dict) -> None
+    def pre_sync(self, import_key: str, **kwargs) -> None:
         """
         This method is called before import process starts
         :param import_key: A key, returned by ClickHouseModel.get_import_key() method
@@ -48,7 +48,7 @@ class Storage:
         """
         pass
 
-    def post_sync(self, import_key, **kwargs):  # type: (str, **dict) -> None
+    def post_sync(self, import_key: str, **kwargs) -> None:
         """
         This method is called after import process has finished.
         :param import_key: A key, returned by ClickHouseModel.get_import_key() method
@@ -57,7 +57,7 @@ class Storage:
         """
         pass
 
-    def post_sync_failed(self, import_key, **kwargs):  # type: (str, **dict) -> None
+    def post_sync_failed(self, import_key: str, **kwargs) -> None:
         """
         This method is called after import process has finished with exception.
         :param import_key: A key, returned by ClickHouseModel.get_import_key() method
@@ -66,7 +66,7 @@ class Storage:
         """
         pass
 
-    def post_batch_removed(self, import_key, batch_size):  # type: (str, int) -> None
+    def post_batch_removed(self, import_key: str, batch_size: int) -> None:
         """
         This method marks that batch has been removed in statsd
         :param import_key: A key, returned by ClickHouseModel.get_import_key() method
@@ -76,8 +76,7 @@ class Storage:
         key = "%s.sync.%s.queue" % (config.STATSD_PREFIX, import_key)
         statsd.gauge(key, self.operations_count(import_key))
 
-    def operations_count(self, import_key, **kwargs):
-        # type: (str, **dict) -> int
+    def operations_count(self, import_key: str, **kwargs) -> int:
         """
         Returns sync queue size
         :param import_key: A key, returned by ClickHouseModel.get_import_key() method
@@ -86,8 +85,7 @@ class Storage:
         """
         raise NotImplemented()
 
-    def get_operations(self, import_key, count, **kwargs):
-        # type: (str, int, **dict) -> List[Tuple[str, str]]
+    def get_operations(self, import_key: str, count: int, **kwargs) -> List[Tuple[str, str]]:
         """
         Must return a list of operations on the model.
         Method should be error safe - if something goes wrong, import data should not be lost.
@@ -98,7 +96,7 @@ class Storage:
         """
         raise NotImplemented()
 
-    def register_operations(self, import_key, operation, *pks):  # type: (str, str, *Any) -> int
+    def register_operations(self, import_key: str, operation: str, *pks: Any) -> int:
         """
         Registers new incoming operation
         :param import_key: A key, returned by ClickHouseModel.get_import_key() method
@@ -108,8 +106,7 @@ class Storage:
         """
         raise NotImplementedError()
 
-    def register_operations_wrapped(self, import_key, operation, *pks):
-        # type: (str, str, *Any)  -> int
+    def register_operations_wrapped(self, import_key: str, operation: str, *pks: Any) -> int:
         """
         This is a wrapper for register_operation method, checking main parameters.
         This method should be called from inner functions.
@@ -140,14 +137,14 @@ class Storage:
         """
         raise NotImplemented()
 
-    def get_last_sync_time(self, import_key):  # type: (str) -> Optional[datetime.datetime]
+    def get_last_sync_time(self, import_key: str) -> Optional[datetime.datetime]:
         """
         Gets the last time, sync has been executed
         :return: datetime.datetime if last sync has been. Otherwise - None.
         """
         raise NotImplemented()
 
-    def set_last_sync_time(self, import_key, dt):  # type: (str, datetime.datetime) -> None
+    def set_last_sync_time(self, import_key: str, dt: datetime.datetime) -> None:
         """
         Sets successful sync time
         :return: None
diff --git a/src/django_clickhouse/tasks.py b/src/django_clickhouse/tasks.py
index 562fbdc..b23baed 100644
--- a/src/django_clickhouse/tasks.py
+++ b/src/django_clickhouse/tasks.py
@@ -11,14 +11,14 @@ from .utils import get_subclasses
 
 
 @shared_task(queue=config.CELERY_QUEUE)
-def sync_clickhouse_model(cls):  # type: (ClickHouseModel) -> None
+def sync_clickhouse_model(model_cls) -> None:
     """
     Syncs one batch of given ClickHouseModel
-    :param cls: ClickHouseModel subclass
+    :param model_cls: ClickHouseModel subclass
     :return: None
     """
-    cls.get_storage().set_last_sync_time(cls.get_import_key(), datetime.datetime.now())
-    cls.sync_batch_from_storage()
+    model_cls.get_storage().set_last_sync_time(model_cls.get_import_key(), datetime.datetime.now())
+    model_cls.sync_batch_from_storage()
 
 
 @shared_task(queue=config.CELERY_QUEUE)
diff --git a/src/django_clickhouse/utils.py b/src/django_clickhouse/utils.py
index a279d3a..1ab1e90 100644
--- a/src/django_clickhouse/utils.py
+++ b/src/django_clickhouse/utils.py
@@ -18,7 +18,7 @@ from .database import connections
 T = TypeVar('T')
 
 
-def get_tz_offset(db_alias=None):  # type: (Optional[str]) -> int
+def get_tz_offset(db_alias: Optional[str] = None) -> int:
     """
     Returns ClickHouse server timezone offset in minutes
     :param db_alias: The database alias used
@@ -28,8 +28,8 @@ def get_tz_offset(db_alias=None):  # type: (Optional[str]) -> int
     return int(db.server_timezone.utcoffset(datetime.datetime.utcnow()).total_seconds() / 60)
 
 
-def format_datetime(dt, timezone_offset=0, day_end=False, db_alias=None):
-    # type: (Union[datetime.date, datetime.datetime], int, bool, Optional[str]) -> str
+def format_datetime(dt: Union[datetime.date, datetime.datetime], timezone_offset: int = 0, day_end: bool = False,
+                    db_alias: Optional[str] = None) -> str:
     """
     Formats datetime and date objects to format that can be used in WHERE conditions of query
     :param dt: datetime.datetime or datetime.date object
@@ -58,9 +58,9 @@ def format_datetime(dt, timezone_offset=0, day_end=False, db_alias=None):
     return server_dt.strftime("%Y-%m-%d %H:%M:%S")
 
 
-def module_exists(module_name):  # type: (str) -> bool
+def module_exists(module_name: str) -> bool:
     """
-    Checks if moudle exists
+    Checks if module exists
     :param module_name: Dot-separated module name
     :return: Boolean
     """
@@ -69,7 +69,7 @@ def module_exists(module_name):  # type: (str) -> bool
     return spam_spec is not None
 
 
-def lazy_class_import(obj):  # type: (Union[str, Any]) -> Any
+def lazy_class_import(obj: Union[str, Any]) -> Any:
     """
     If string is given, imports object by given module path.
     Otherwise returns the object
@@ -88,7 +88,7 @@ def lazy_class_import(obj):  # type: (Union[str, Any]) -> Any
         return obj
 
 
-def get_subclasses(cls, recursive=False):  # type: (T, bool) -> Set[T]
+def get_subclasses(cls: T, recursive: bool = False) -> Set[T]:
     """
     Gets all subclasses of given class
     Attention!!! Classes would be found only if they were imported before using this function
@@ -105,8 +105,8 @@ def get_subclasses(cls, recursive=False):  # type: (T, bool) -> Set[T]
     return subclasses
 
 
-def model_to_dict(instance, fields=None, exclude_fields=None):
-    # type: (DjangoModel, Optional[Iterable[str]], Optional[Iterable[str]]) -> Dict[str, Any]
+def model_to_dict(instance: DjangoModel, fields:  Optional[Iterable[str]] = None,
+                  exclude_fields:  Optional[Iterable[str]] = None) -> Dict[str, Any]:
     """
     Standard model_to_dict ignores some fields if they have invalid naming
     :param instance: Object to convert to dictionary