message: Fix tpu_strategy.py's bug which may add list with tuple when _packed_variable is not None.
diff: @@ -1176,7 +1176,7 @@ class TPUExtended(distribute_lib.StrategyExtendedV1):
  if isinstance(
  value,
  values.DistributedVariable) and value._packed_variable is not None:
  - value_list = tuple(
  + value_list = list(
  value._packed_variable.on_device(d)
  for d in value._packed_variable.devices)
  # pylint: enable=protected-access
  