code: protected function createTransactionNode()
      {
          $xml = new DOMDocument();
          $xml->formatOutput = true;
  
          $trxRef = $xml->appendChild($xml->createElement('TransactionReference'));
  
          if (null !== $this->context) {
              $trxRef->appendChild($xml->createElement('CustomerContext', $this->context));
          }
  
          return $trxRef->cloneNode(true);
      }
docs: Creates the TransactionReference node for a request.
  
  @return \DomNode