code: protected function _xpath($xpath)
      {
          $use_errors = libxml_use_internal_errors(true);
  
          $nodes = $this->xpath($xpath);
  
          libxml_use_internal_errors($use_errors);
  
          if ($nodes === false) {
              throw new InvalidArgumentException('Invalid XPath expression ' . $xpath);
          }
  
          return $nodes;
      }
docs: #@+
  @ignore
  @param $xpath
  @throws InvalidArgumentException
  @return \SimpleXMLElement[]