code: def _polling_cookie(self):
          
          parsed_url = urlparse(self._response.request.url)
          host = parsed_url.hostname.strip('.')
          if host == 'localhost':
              return {'cookie': self._response.headers.get('set-cookie', '')}
          return {}
docs: Collect retry cookie - we only want to do this for the test server
          at this point, unless we implement a proper cookie policy.
  
          :returns: Dictionary containing a cookie header if required,
           otherwise an empty dictionary.