code: def get_default_field_names(self, declared_fields, model_info):
          
          return (
              [self.url_field_name] +
              list(declared_fields.keys()) +
              list(model_info.fields.keys()) +
              list(model_info.forward_relations.keys())
          )
docs: Return the default list of field names that will be used if the
          `Meta.fields` option is not specified.