code: protected function makeDomXpath($response)
      {
          $domDoc = $this->loadDomDocument($response);
          $domXpath = new \DOMXPath($domDoc);
  
          $domXpath->registerNamespace(
              self::XMLNS_PREFIX,
              $domDoc->documentElement->lookupNamespaceUri(null)
          );
  
          return $domXpath;
      }
docs: Make a Xpath-queryable object for an XML string
  
  registers TNS namespace with prefix self::XMLNS_PREFIX
  
  @param string $response
  @return \DOMXPath
  @throws Exception when there's a problem loading the message