code: def allreduce(*inputs):
      """Cross GPU all reduce autograd operation for calculate mean and
      variance in SyncBN.
      """
      return AllReduce.apply(*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 a global function with example usage: allreduce() and returns: AllReduce