code: def _refresh(self, http):
          
          try:
              self._retrieve_info(http)
              self.access_token, self.token_expiry = _metadata.get_token(
                  http, service_account=self.service_account_email)
          except http_client.HTTPException as err:
              raise client.HttpAccessTokenRefreshError(str(err))
docs: Refreshes the access token.
  
          Skip all the storage hoops and just refresh using the API.
  
          Args:
              http: an object to be used to make HTTP requests.
  
          Raises:
              HttpAccessTokenRefreshError: When the refresh fails.