docs: def fusion_append(fields, error_field, etl_func):
      """
      TODO: dict based better than list based please
  
      :param fields:
      :param error_field:
      :param etl_func:
      :return:
      """
      return compose(read_fields(fields),
                     etl_func, dict_enforcer, write_error_field(error_field))