protected function findNamespace($nsFragment)
 {
     $returnValue = '';
     if (is_null($this->item)) {
         foreach ($this->queryXPath('namespace::*') as $node) {
             $name = preg_replace('/xmlns(:)?/', '', $node->nodeName);
             $uri = $node->nodeValue;
             if (strpos($uri, $nsFragment) > 0) {
                 $returnValue = $name;
                 break;
             }
         }
     } else {
         $namespaces = $this->item->getNamespaces();
         foreach ($namespaces as $name => $uri) {
             if (strpos($uri, $nsFragment) > 0) {
                 $returnValue = $name;
                 break;
             }
         }
         if ($returnValue === '') {
             $returnValue = $this->recursivelyFindNamespace($this->data, $nsFragment);
         }
     }
     return $returnValue;
 }