message: fix bug of lacking axis when using array.ops.concat in unwrap_and_concat function
diff: @@ -1653,7 +1653,7 @@ def _combine_distributed_scaffold(grouped_scaffold, distribution):
  def _unwrap_and_concat(value):
  value = nest.flatten(distribution.unwrap(value))
  if len(value) != 1:
  - return array_ops.concat(value)
  + return array_ops.concat(value, 0)
  return value[0]
  ready_op = distribution.call_for_each_tower(
  