code: def _file_exists(path, filename):
      """Checks if the filename exists under the path."""
      return os.path.isfile(os.path.join(path, filename))
  
imports: import csv
  import os
  import tarfile
  from tensorflow.compat.v1 import estimator
  import tqdm
  from tensor2tensor.data_generators import generator_utils
  from tensor2tensor.data_generators import problem
  from tensor2tensor.data_generators import speech_recognition
  from tensor2tensor.utils import registry
label_desc: Use image node_id 2 for calling a global function with example usage: _file_exists(path, filename) and returns: os