/**
  * @see EPSInterface::createBillOfLading()
  */
 public function createBillOfLading($sessionId, $picking)
 {
     try {
         $createBillOfLadingStdObject = new stdClass();
         $createBillOfLadingStdObject->sessionId = $sessionId;
         $createBillOfLadingStdObject->picking = $picking->toStdClass();
         $response = parent::createBillOfLading($createBillOfLadingStdObject);
         if (isset($response->return)) {
             $resultBOL = new ResultBOL($response->return);
         } else {
             $resultBOL = null;
         }
         return $resultBOL;
     } catch (SoapFault $sf) {
         throw new ServerException($sf);
     }
 }