class_docstr: The async pipeline parallelism for Pipe.
class_docstr_tok: ["The","async","pipeline","parallelism","for","Pipe","."]
code: def back_helper(self, output: List[Batch]) -> None:
      pass
  
file_path: fairscale/fairscale/nn/pipe/async_pipeline.py
imports: import logging
  import os
  from threading import Event
  from typing import Dict, List, Optional, Union
  import torch
  from .async_schedule import AsyncEventLoop, ModuleWrapper
  from .messages import MakeTransport
  from .microbatch import Batch
  from .skip.layout import SkipLayout
  from .skip.tracker import SkipTrackerThroughPotals
label_desc: Use image node_id 4 for calling the AsyncPipeline obj's underlying member method code with example usage: obj.back_helper(output) without return types