code: def change_and_save(self, update_only_changed_fields=False, **changed_fields):
          
          change_and_save(self, update_only_changed_fields=update_only_changed_fields, **changed_fields)
          return self
docs: Changes a given `changed_fields` on this object, saves it and returns itself.
          :param update_only_changed_fields: only changed fields will be updated in the database.
          :param changed_fields: fields to change.
          :return: self