code: def set_content_model(self):
          
          if not self.content_model:
              is_base_class = (
                  base_concrete_model(ContentTyped, self) == self.__class__)
              self.content_model = (
                  None if is_base_class else self.get_content_model_name())
docs: Set content_model to the child class's related name, or None if this is
          the base class.