docs: def append_response(self, response):
          """Append the response to the stack of responses.
  
          :param tornado.httpclient.HTTPResponse response: The HTTP response
  
          """
          self._responses.append(response)
          if 'Warning' in response.headers:
              LOGGER.warning(
                  'HTTP %s %s Warning (%s): %s (attempt %s)',
                  response.request.method, response.request.url,
                  response.code, response.headers['Warning'],
                  len(self._responses))