code: def reduce_tensor(tensor):
      rt = tensor.clone()
      dist.all_reduce(rt, op=dist.reduce_op.SUM)
      rt /= args.world_size
      return rt
  
file_path: DALI/dali/test/python/test_RN50_external_source_parallel_train_ddp.py
imports: import os
  import time
  import torch
  import torch.distributed
  import torch.nn
  import torch.optim
  import torchvision.models
  from nvidia.dali.plugin.base_iterator import LastBatchPolicy
  from nvidia.dali.plugin.pytorch import DALIClassificationIterator
  from torch.nn.parallel import DistributedDataParallel
  from test_RN50_external_source_parallel_utils import parse_test_arguments, external_source_parallel_pipeline, external_source_pipeline, file_reader_pipeline, get_pipe_factories
  from test_utils import AverageMeter
label_desc: Use image node_id 1 for calling a global function with example usage: reduce_tensor(tensor) and returns: rt