code: def _check_response_for_request_errors(self):
          
          if self.response.HighestSeverity == "ERROR":
              for notification in self.response.Notifications:  # pragma: no cover
                  if notification.Severity == "ERROR":
                      if "Postal Code Not Found" in notification.Message:
                          raise FedexPostalCodeNotFound(notification.Code,
                                                        notification.Message)
  
                      elif "Invalid Postal Code Format" in self.response.Notifications:
                          raise FedexInvalidPostalCodeFormat(notification.Code,
                                                             notification.Message)
                      else:
                          raise FedexError(notification.Code,
                                           notification.Message)
docs: Checks the response to see if there were any errors specific to
          this WSDL.