public static function get_user_attempts_parameters() {
        return new external_function_parameters (
            array(
                'quizid' => new external_value(PARAM_INT, 'quiz instance id'),
                'userid' => new external_value(PARAM_INT, 'user id, empty for current user', VALUE_DEFAULT, 0),
                'status' => new external_value(PARAM_ALPHA, 'quiz status: all, finished or unfinished', VALUE_DEFAULT, 'finished'),
                'includepreviews' => new external_value(PARAM_BOOL, 'whether to include previews or not', VALUE_DEFAULT, false),

            )
        );
    }