code: def object(self, session):
          '''Instance of :attr:`model_type` with id :attr:`object_id`.'''
          if not hasattr(self, '_object'):
              pkname = self.model_type._meta.pkname()
              query = session.query(self.model_type).filter(**{pkname:
                                                               self.object_id})
              return query.items(callback=self.__set_object)
          else:
              return self._objecf object(self, session):
          '''Instance of :attr:`model_type` with id :attr:`object_id`.'''
          if not hasattr(self, '_object'):
              pkname = self.model_type._meta.pkname()
              query = session.query(self.model_type).filter(**{pkname:
                                                               self.object_id})
              return query.items(callback=self.__set_object)
          else:
              return self._object
docs: Instance of :attr:`model_type` with id :attr:`object_id`.