class_docstr: Subclass Tornado Future, reinstating cancellation.
code: def cancelled(self):
      return self.done() and isinstance(
          self.exception(), CancelledError
      )
  
imports: import zmq
  from zmq._future import _AsyncPoller, _AsyncSocket
  from tornado.concurrent import Future
  from tornado.ioloop import IOLoop
label_desc: Use image node_id 2 for calling the _TornadoFuture obj's underlying member method code with example usage: obj.cancelled() and returns: unknown