Implement first simple working function and tests

tests/informal.py

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+from sqlalchemy.engine.create import create_engine
+from sqlalchemy.orm import declarative_base, relationship
+from sqlalchemy.orm.session import Session
+from sqlalchemy.sql.functions import now as db_now
+from sqlalchemy.sql.schema import Column, ForeignKey as FKey
+from sqlalchemy.sql.sqltypes import Integer, String, TIMESTAMP, Unicode
+
+from orm2pydantic.sqla import from_sqla
+
+
+ORMBase = declarative_base()
+engine = create_engine("sqlite://")
+
+
+def default_factory() -> str: return '1'
+
+
+class AbstractBase(ORMBase):
+    __abstract__ = True
+
+    NON_REPR_FIELDS = ['id', 'date_created', 'date_updated']
+
+    date_created = Column(TIMESTAMP(timezone=False), server_default=db_now())
+    date_updated = Column(TIMESTAMP(timezone=False), server_default=db_now(), onupdate=db_now())
+
+
+class StateProvince(AbstractBase):
+    __tablename__ = 'state_province'
+
+    id = Column(Integer, primary_key=True)
+    country = Column(String(2), nullable=False, index=True)
+    name = Column(Unicode(255), nullable=False, index=True)
+
+    cities = relationship('City', backref='state_province', lazy='selectin')
+
+
+class City(AbstractBase):
+    __tablename__ = 'city'
+
+    id = Column(Integer, primary_key=True)
+    state_province_id = Column(Integer, FKey('state_province.id', ondelete='RESTRICT'), index=True)
+    zip_code = Column(String(5), nullable=False, index=True)
+    name = Column(Unicode(255), nullable=False, index=True)
+
+    streets = relationship('Street', backref='city', lazy='selectin')
+
+
+class Street(AbstractBase):
+    __tablename__ = 'street'
+
+    id = Column(Integer, primary_key=True)
+    city_id = Column(Integer, FKey('city.id', ondelete='RESTRICT'), index=True)
+    name = Column(Unicode(255), nullable=False, index=True)
+
+    addresses = relationship('Address', backref='street', lazy='selectin')
+
+
+class Address(AbstractBase):
+    __tablename__ = 'address'
+
+    id = Column(Integer, primary_key=True)
+    street_id = Column(Integer, FKey('street.id', ondelete='RESTRICT'), index=True)
+    house_number = Column(String(8), nullable=False, default=default_factory)
+    supplement = Column(String(255))
+
+
+def main_test() -> None:
+    AbstractBase.metadata.create_all(engine)
+
+    from_sqla(StateProvince)
+    from_sqla(City)
+    from_sqla(Street)
+    _PydanticAddress = from_sqla(Address)
+
+    with Session(engine) as session:
+        bavaria = StateProvince(country="de", name="Bavaria")
+        munich = City(zip_code='80333', name="Munich")
+        bavaria.cities.append(munich)
+        maximilian_street = Street(name="Maximilianstrasse")
+        munich.streets.append(maximilian_street)
+        some_address = Address()
+        maximilian_street.addresses.append(some_address)
+        session.add_all([bavaria, munich, maximilian_street, some_address])
+        session.commit()
+
+        address = _PydanticAddress.from_orm(some_address)
+
+    assert address.house_number == '1'
+    assert address.street.city.state_province.name == "Bavaria"
+
+
+if __name__ == '__main__':
+    main_test()