class_docstr: An autograd function that performs allgather on a tensor.
code: def backward(ctx, grad_output):
      return (
          grad_output[
              ctx.batch_size
              * ctx.rank : ctx.batch_size
              * (ctx.rank + 1)
          ],
          None,
      )
  
imports: import logging
  import torch
  from torch import nn
  import torch.nn.functional
  import math
label_desc: Use image node_id 2 for calling the AllGather obj's underlying member method code with example usage: obj.backward(ctx, grad_output) and returns: grad_output,  None