public static function exportList($xml)
    {
        $app = Application::getFacadeApplication();
        $db = $app->make(Connection::class);
        $bxml = $xml->addChild('blocktypesets');
        $rs = $db->executeQuery('select btsID from BlockTypeSets order by btsID asc');
        while (($btsID = $rs->fetchColumn()) !== false) {
            $bts = static::getByID($btsID);
            $bts->export($bxml);
        }
    }