/**
  * Updates metadata with the authorization token.
  *
  * @param array $metadata metadata hashmap
  * @param string $authUri optional auth uri
  * @param callable $httpHandler callback which delivers psr7 request
  *
  * @return array updated metadata hashmap
  */
 public function updateMetadata($metadata, $authUri = null, callable $httpHandler = null)
 {
     if (empty($authUri)) {
         return $metadata;
     }
     $this->auth->setAudience($authUri);
     return parent::updateMetadata($metadata, $authUri, $httpHandler);
 }