public static function set_user_flags_returns() {
        return new external_multiple_structure(
            new external_single_structure(
                array(
                    'id' => new external_value(PARAM_INT, 'id of record if successful, -1 for failure'),
                    'userid' => new external_value(PARAM_INT, 'userid of record'),
                    'errormessage' => new external_value(PARAM_TEXT, 'Failure error message', VALUE_OPTIONAL)
                )
            )
        );
    }