code: def open_if_master(path, mode):
      from mmf.utils.file_io import PathManager
  
      if is_main():
          return PathManager.open(path, mode)
      else:
          return contextlib.nullcontext()
  
imports: import contextlib
  import logging
  import os
  import pickle
  import socket
  import subprocess
  import warnings
  from itertools import chain
  import torch
  from mmf.common.registry import registry
  from torch import distributed
label_desc: Use image node_id 20 for calling a global function with example usage: open_if_master(path, mode) and returns: PathManager, contextlib