docs: def create_or_update(self,
                           identifier: Identifier,
                           data: Dict[str, Any],
                           ) -> Tuple[object, bool]:
          """
          Create or update a model.
  
          :param identifier: An object with :attr:`class_name` and :attr:`key`
                             attributes
          :param data: A dictionary keyed by column name, with values being the
                       converted values to set on the model instance
          :return: A two-tuple of model instance and whether or not it was created.
          """
          raise NotImplementedError