message: Fix the bug in python3 the devices list in multi_worker_strategy becomes `dict_values`.
diff: @@ -121,7 +121,7 @@ class MultiWorkerMirroredStrategy(MirroredStrategy):
  worker: [device_util.canonicalize(worker, '/device:CPU:0')]
  for worker in self._workers
  }
  - self._devices = nest.flatten(self._worker_device_map.values())
  + self._devices = nest.flatten(self._worker_device_map)
  super(MultiWorkerMirroredStrategy, self).__init__(
  devices=self._devices, prefetch_on_device=prefetch_on_device)
  