Added simple flask example

examples/flask_sqlalchemy/README.md

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+Cookbook Example Django Project
+===============================
+
+This example project demos integration between Graphene, Flask and SQLAlchemy.
+The project contains two models, one named `Department` and another
+named `Employee`.
+
+Getting started
+---------------
+
+First you'll need to get the source of the project. Do this by cloning the
+whole Graphene repository:
+
+```bash
+# Get the example project code
+git clone https://github.com/graphql-python/graphene.git
+cd graphene/examples/cookbook
+```
+
+It is good idea (but not required) to create a virtual environment
+for this project. We'll do this using
+[virtualenv](http://docs.python-guide.org/en/latest/dev/virtualenvs/)
+to keep things simple,
+but you may also find something like
+[virtualenvwrapper](https://virtualenvwrapper.readthedocs.org/en/latest/)
+to be useful:
+
+```bash
+# Create a virtualenv in which we can install the dependencies
+virtualenv env
+source env/bin/activate
+```
+
+Now we can install our dependencies:
+
+```bash
+pip install -r requirements.txt
+```
+
+Now the following command will setup the database, and start the server:
+
+```bash
+./app.py
+
+```
+
+
+Now head on over to
+[http://127.0.0.1:5000/](http://127.0.0.1:5000/)
+and run some queries!

examples/flask_sqlalchemy/app.py

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+import json
+from flask import Flask
+from database import db_session, init_db
+
+from schema import schema, Department
+
+app = Flask(__name__)
+
+
+@app.route('/')
+def hello_world():
+    query = '{node(id:"%s"){name, employees { edges { node {name} } } } }' % Department.global_id(1)
+    return json.dumps(schema.execute(query).data)
+
+
+@app.teardown_appcontext
+def shutdown_session(exception=None):
+    db_session.remove()
+
+if __name__ == '__main__':
+    init_db()
+    app.run()

examples/flask_sqlalchemy/database.py

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+from sqlalchemy import create_engine
+from sqlalchemy.orm import scoped_session, sessionmaker
+from sqlalchemy.ext.declarative import declarative_base
+
+engine = create_engine('sqlite:///database.sqlite3', convert_unicode=True)
+db_session = scoped_session(sessionmaker(autocommit=False,
+                                         autoflush=False,
+                                         bind=engine))
+Base = declarative_base()
+Base.query = db_session.query_property()
+
+
+def init_db():
+    # import all modules here that might define models so that
+    # they will be registered properly on the metadata.  Otherwise
+    # you will have to import them first before calling init_db()
+    from models import Department, Employee
+    Base.metadata.drop_all(bind=engine)
+    Base.metadata.create_all(bind=engine)
+
+    department = Department(name='Informatics')
+    db_session.add(department)
+
+    db_session.add(department)
+    employee = Employee(name='Peter', department=department)
+    db_session.add(employee)
+    db_session.commit()

examples/flask_sqlalchemy/models.py

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+from database import Base
+from sqlalchemy import Column, DateTime, String, Integer, ForeignKey, func
+from sqlalchemy.orm import relationship, backref
+
+
+class Department(Base):
+    __tablename__ = 'department'
+    id = Column(Integer, primary_key=True)
+    name = Column(String)
+
+
+class Employee(Base):
+    __tablename__ = 'employee'
+    id = Column(Integer, primary_key=True)
+    name = Column(String)
+    # Use default=func.now() to set the default hiring time
+    # of an Employee to be the current time when an
+    # Employee record was created
+    hired_on = Column(DateTime, default=func.now())
+    department_id = Column(Integer, ForeignKey('department.id'))
+    # Use cascade='delete,all' to propagate the deletion of a Department onto its Employees
+    department = relationship(
+        Department,
+        backref=backref('employees',
+                        uselist=True,
+                        cascade='delete,all'))

examples/flask_sqlalchemy/requirements.txt

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+graphene[sqlalchemy]
+SQLAlchemy==1.0.11
+Flask==0.10.1

examples/flask_sqlalchemy/schema.py

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+import graphene
+from graphene import relay
+from graphene.contrib.sqlalchemy import SQLAlchemyNode
+from models import Department as DepartmentModel, Employee as EmployeeModel
+
+from database import db_session
+
+schema = graphene.Schema(session=db_session)
+
+
+@schema.register
+class Department(SQLAlchemyNode):
+    class Meta:
+        model = DepartmentModel
+
+
+@schema.register
+class Employee(SQLAlchemyNode):
+    class Meta:
+        model = EmployeeModel
+
+
+class Query(graphene.ObjectType):
+    node = relay.NodeField(Department, Employee)
+
+schema.query = Query