docs: def _validate_entity_cls(self, entity_cls):
          """Validate that Entity is a valid class"""
          # Import here to avoid cyclic dependency
          from protean.core.entity import Entity
  
          if not issubclass(entity_cls, Entity):
              raise AssertionError(
                  f'Entity {entity_cls.__name__} must be subclass of `Entity`')
  
          if entity_cls.meta_.abstract is True:
              raise NotSupportedError(
                  f'{entity_cls.__name__} class has been marked abstract'
                  f' and cannot be instantiated')