code: def set(self, refresh_token):
          
          logger.info('Saving refresh_token to %s', repr(self._filename))
          try:
              with open(self._filename, 'w') as f:
                  f.write(refresh_token)
          except IOError as e:
              logger.warning('Failed to save refresh_token: %s', e)
docs: Cache a refresh token, ignoring any failure.
  
          Args:
              refresh_token (str): Refresh token to cache.