public static function get_user_id_for_uniqueid_static($assignid, $uniqueid) {
        global $DB;

        // Search for a record.
        if ($record = $DB->get_record('assign_user_mapping',
                                      array('assignment'=>$assignid, 'id'=>$uniqueid),
                                      'userid',
                                      IGNORE_MISSING)) {
            return $record->userid;
        }

        return false;
    }