code: private function createRequestLandedCost(LandedCostRequest $landedCostRequest)
      {
          $xml = new DOMDocument();
          $xml->formatOutput = true;
  
          $tradeabilityRequest = $xml->appendChild($xml->createElement('LandedCostRequest'));
          $tradeabilityRequest->setAttribute('xml:lang', 'en-US');
  
          $request = $tradeabilityRequest->appendChild($xml->createElement('Request'));
  
          $node = $xml->importNode($this->createTransactionNode(), true);
          $request->appendChild($node);
  
          $request->appendChild($xml->createElement('RequestAction', 'LandedCost'));
  
          if ($landedCostRequest->getQueryRequest() !== null) {
              $tradeabilityRequest->appendChild($landedCostRequest->getQueryRequest()->toNode($xml));
          }
  
          return $xml->saveXML();
      }
docs: Create the LandedCostRequest request.
  
  @param LandedCostRequest $landedCostRequest The request details. Refer to the UPS documentation for available structure
  
  @return string