code: def async_send(self, url, data, headers, success_cb, failure_cb):
          
          # this can be optimized by making a custom self.send that does not
          # read the response since we don't use it.
          self._lock.acquire()
          return gevent.spawn(
              super(GeventedHTTPTransport, self).send, url, data, headers
          ).link(lambda x: self._done(x, success_cb, failure_cb))
docs: Spawn an async request to a remote webserver.