code: def _token_valid(self):
          
          if not self._cache_token:
              return False
          now = time.time()
          if now - self._token.acquired_time > self._token_timeout:
              logger.debug('token needs to be reset')
              return False
          return True
docs: checks if the token cached is valid or has expired by comparing
          the time token was created with current time
          :return: True if token has not expired yet and False is token is empty or
                  it has expired