code: def _add_timeout(self, request, future):
          
          io_loop = IOLoop.current()
          t = io_loop.call_later(
              request.ttl,
              self._request_timed_out,
              request.id,
              request.service,
              request.ttl,
              future,
          )
          io_loop.add_future(future, lambda f: io_loop.remove_timeout(t))
docs: Adds a timeout for the given request to the given future.