text: from __future__ import unicode_literals
  
  import six
  import sqlalchemy as sa
  from sqlalchemy.ext.hybrid import hybrid_property
  
  from sqlalchemy_utils import generic_relationship
  from tests import TestCase
  
  
  class TestGenericRelationship(TestCase):
      def create_models(self):
          class User(self.Base):
              __tablename__ = 'user'
              id = sa.Column(sa.Integer, primary_key=True)
  
          class UserHistory(self.Base):
              __tablename__ = 'user_history'
              id = sa.Column(sa.Integer, primary_key=True)
  
              transaction_id = sa.Column(sa.Integer, primary_key=True)
  
          class Event(self.Base):
              __tablename__ = 'event'
              id = sa.Column(sa.Integer, primary_key=True)
  
              transaction_id = sa.Column(sa.Integer)
  
              object_type = sa.Column(sa.Unicode(255))
              object_id = sa.Column(sa.Integer, nullable=False)
  
              object = generic_relationship(
                  object_type, object_id
              )
  
              @hybrid_property
              def object_version_type(self):
                  return self.object_type + 'History'
  
              @object_version_type.expression
              def object_version_type(cls):
                  return sa.func.concat(cls.object_type, 'History')
  
              object_version = generic_relationship(
                  object_version_type, (object_id, transaction_id)
              )
  
          self.User = User
          self.UserHistory = UserHistory
          self.Event = Event
  
      def test_set_manual_and_get(self):
          user = self.User(id=1)
          history = self.UserHistory(id=1, transaction_id=1)
          self.session.add(user)
          self.session.add(history)
          self.session.commit()
  
          event = self.Event(transaction_id=1)
          event.object_id = user.id
          event.object_type = six.text_type(type(user).__name__)
          assert event.object is None
  
          self.session.add(event)
          self.session.commit()
  
          assert event.object == user
          assert event.object_version == history
  