private function initializeFrom(XMLReader $reader)
 {
     if ($reader->nodeType !== XMLReader::ELEMENT) {
         $node = new XMLReaderNode($reader);
         throw new RuntimeException(sprintf('Reader must be at an XMLReader::ELEMENT, is XMLReader::%s given.', $node->getNodeTypeName()));
     }
     $this->name_ = $reader->name;
     $this->attributes_ = parent::getAttributes()->getArrayCopy();
 }