code: def _index_file_exists(idx_fn):
      """Helper function to test if index file exists"""
      if os.path.exists(idx_fn + ".npy") and os.path.exists(
          idx_fn + ".info"
      ):
          return True
      else:
          return False
  
imports: import datetime
  import json
  import multiprocessing
  import os
  import pickle
  import time
  from functools import partial
  from typing import Callable, List, Optional, Type
  import numpy
  import torch
  from nemo.core import Dataset
  from nemo.utils import AppState, logging
label_desc: Use image node_id 2 for calling a global function with example usage: _index_file_exists(idx_fn) and returns: True, False