protected function convertToString($data)
 {
     $domDocument = $this->getDomDocument();
     $result = @$domDocument->loadXML($data);
     if (true === $result) {
         if (0 < count($this->getXPathRules())) {
             $domDocument = $this->sanitizeXML($domDocument);
         }
         $formattedXML = @$domDocument->saveXML() . "\n";
         return $formattedXML;
     } else {
         return parent::convertToString($data);
     }
 }