message: Set number of parallel_iterations for the while loop to be 1 to enable input data to be processed sequentially by the `reduce` call.
diff: @@ -382,7 +382,7 @@ class _IterableInput(object):
  return has_data, data, state
  has_data, data, final_state = control_flow_ops.while_loop(
  - cond, loop_body, [has_data, data, initial_state])
  + cond, loop_body, [has_data, data, initial_state], parallel_iterations=1)
  return final_state
  