code: def backward(ctx, gradOutput):
      return Broadcast.apply(ctx.target_gpus, gradOutput)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import functools
  import threading
  import torch
  import torch.cuda.comm
  from torch.autograd import Variable, Function
  from torch.nn.parallel.data_parallel import DataParallel
  from torch.nn.parallel.parallel_apply import get_a_var
  from torch.nn.parallel._functions import ReduceAddCoalesced, Broadcast
label_desc: Use image node_id 2 for calling the Reduce obj's underlying member method code with example usage: obj.backward(ctx, gradOutput) and returns: Broadcast