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