code: def backward(ctx: Any, *grad_output: Tensor) -> Tuple[None, Tensor]:
      return (None, _AllToAll.apply(ctx.group, *grad_output))
  
file_path: fairscale/fairscale/nn/moe/moe_layer.py
imports: from typing import TYPE_CHECKING, Any, Optional, Tuple, Union, cast
  import torch
  from torch import Tensor
  import torch.distributed
  from torch.nn import Module, ModuleList
label_desc: Use image node_id 2 for calling the _AllToAll obj's underlying member method code with example usage: obj.backward(ctx) and returns: None,  _AllToAll