code: def forward(ctx, *inputs):
      ctx.target_gpus = [
          inputs[i].get_device() for i in range(len(inputs))
      ]
      inputs = sorted(inputs, key=lambda i: i.get_device())
      return comm.reduce_add(inputs)
  
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 1 for calling the Reduce obj's underlying member method code with example usage: obj.forward(ctx) and returns: comm