public static function save_submission_parameters() {
        global $CFG;
        $instance = new assign(null, null, null);
        $pluginsubmissionparams = array();

        foreach ($instance->get_submission_plugins() as $plugin) {
            if ($plugin->is_visible()) {
                $pluginparams = $plugin->get_external_parameters();
                if (!empty($pluginparams)) {
                    $pluginsubmissionparams = array_merge($pluginsubmissionparams, $pluginparams);
                }
            }
        }

        return new external_function_parameters(
            array(
                'assignmentid' => new external_value(PARAM_INT, 'The assignment id to operate on'),
                'plugindata' => new external_single_structure(
                    $pluginsubmissionparams
                )
            )
        );
    }