code: def backward(ctx, grad_output):
      return (None, None, None) + (
          _Broadcast.apply(ctx.src, ctx.group, grad_output),
      )
  
imports: import torch
  import torch.distributed
  from torch.autograd import Function
label_desc: Use image node_id 2 for calling the _Reduce obj's underlying member method code with example usage: obj.backward(ctx, grad_output) and returns: unknown