/**
  * @param string $rootNodeName
  * @returns DOMElement root node
  */
 static function createDocument($rootNodeName)
 {
     $doc = new \DOMDocument('1.0', 'UTF-8');
     if (Config::isSandboxMode()) {
         $doc->formatOutput = true;
     }
     return $doc->appendChild($doc->createElement($rootNodeName));
 }