message: Clarify ReplicaContext.devices returns a nested list for MS and MWMS.
diff: @@ -2814,8 +2814,15 @@ class ReplicaContext(object):
  return self._strategy
  @property
  + @deprecation.deprecated(None, "Please avoid relying on devices property.")
  def devices(self):
  - """The devices this replica is to be executed on, as a tuple of strings."""
  + """Returns the devices this replica is to be executed on, as a tuple of strings.
  +
  + NOTE: For `tf.distribute.MirroredStrategy` and
  + `tf.distribute.experimental.MultiWorkerMirroredStrategy`, this returns a
  + nested
  + list of device strings, e.g, [["gpu:0"]].
  + """
  require_replica_context(self)
  return (device_util.current(),)
  