def METHOD_NAME(self):
    # When the executor gets lost, the weakref callback will wake up
    # the worker threads.
    def weakref_cb(_, q=self._work_queue):
        q.put(None)
    # TODO(bquinlan): Should avoid creating new threads if there are more
    # idle threads than items in the work queue.
    if len(self._threads) < self._max_workers:
        t = threading.Thread(target=_worker,
                             args=(weakref.ref(self, weakref_cb),
                                   self._work_queue))
        t.daemon = True
        t.start()
        self._threads.add(t)
        _threads_queues[t] = self._work_queue