code: def check_librispeech_folders(data_folder, splits):
      """
      Check if the data folder actually contains the LibriSpeech dataset.
  
      If it does not, an error is raised.
  
      Returns
      -------
      None
  
      Raises
      ------
      OSError
          If LibriSpeech is not found at the specified path.
      """
      # Checking if all the splits exist
      for split in splits:
          split_folder = os.path.join(data_folder, split)
          if not os.path.exists(split_folder):
              err_msg = (
                  "the folder %s does not exist (it is expected in the "
                  "Librispeech dataset)" % split_folder
              )
              raise OSError(err_msg)
  
file_path: speechbrain/recipes/LibriSpeech/Tokenizer/librispeech_prepare.py
imports: import os
  import csv
  import random
  from collections import Counter
  from dataclasses import dataclass
  import functools
  import logging
  from speechbrain.utils.data_utils import download_file, get_all_files
  from speechbrain.dataio.dataio import load_pkl, save_pkl, merge_csvs, read_audio_info
  from speechbrain.utils.parallel import parallel_map
label_desc: Use image node_id 8 for calling a global function with example usage: check_librispeech_folders(data_folder, splits) without return types