docs: def issued_at(self):
          """Time when access token was requested, as seconds since epoch.
  
          Note:
              Accessing this property when there wasn't any request attempts
              will return current time.
  
          Returns:
              int
          """
          issued_at = self._issued_at
          if issued_at is None:
              self._issued_at = int(time.time())
          return self._issued_at