code: public function recoverLabel($trackingData, $labelSpecification = null, $labelDelivery = null, $translate = null)
      {
          if (is_array($trackingData)) {
              if (!isset($trackingData['value'])) {
                  throw new InvalidArgumentException('$trackingData parameter is required to contain `value`.');
              }
  
              if (!isset($trackingData['shipperNumber'])) {
                  throw new InvalidArgumentException('$trackingData parameter is required to contain `shipperNumber`.');
              }
          }
  
          if (!empty($translate)) {
              if (!isset($translateOpts['language'])) {
                  $translateOpts['language'] = 'eng';
              }
  
              if (!isset($translateOpts['dialect'])) {
                  $translateOpts['dialect'] = 'US';
              }
          }
  
          $request = $this->createRecoverLabelRequest($trackingData, $labelSpecification, $labelDelivery, $translate);
          $response = $this->request($this->createAccess(), $request, $this->compileEndpointUrl($this->recoverLabelEndpoint));
  
          if ($response->Response->ResponseStatusCode == 0) {
              throw new Exception(
                  "Failure ({$response->Response->Error->ErrorSeverity}): {$response->Response->Error->ErrorDescription}",
                  (int)$response->Response->Error->ErrorCode
              );
          } else {
              unset($response->Response);
  
              return $this->formatResponse($response);
          }
      }
docs: Recover a shipping label.
  
  @param string|array $trackingData Either the tracking number or a map of ReferenceNumber data
  [value:, shipperNumber:]
  @param array|null $labelSpecification Map of label specification data for this request. Optional.
  [userAgent:, imageFormat: 'HTML|PDF']
  @param array|null $labelDelivery All elements are optional. [link:]
  @param array|null $translate Map of translation data. Optional. [language:, dialect:]
  
  @throws Exception|InvalidArgumentException
  
  @return \stdClass