code: def check_data_folder(root_folder):
      """
      Check if all directories exist to prepare the Switchboard dataset.
  
      Parameters
      ----------
      root_folder : str
          Root directory, where the Switchboard data is located.
          Expects the following subdirectories to exist:
          "docs", "swb1_d1", "swb1_d2", "swb1_d3", "swb1_d4"
      """
      for sub_folder in [
          "docs",
          "swb1_d1",
          "swb1_d2",
          "swb1_d3",
          "swb1_d4",
      ]:
          swbd_folder = os.path.join(root_folder, sub_folder)
          if not os.path.exists(swbd_folder):
              err_msg = f"The folder {swbd_folder} does not exist (it is expected in the Switchboard dataset)"
              raise OSError(err_msg)
  
imports: import re
  import csv
  import logging
  import os
  from collections import defaultdict
  from speechbrain.dataio.dataio import merge_csvs
  from speechbrain.utils.data_utils import download_file, get_all_files
label_desc: Use image node_id 4 for calling a global function with example usage: check_data_folder(root_folder) without return types