code: def check_already_generated(md_dir, aishell1_dir):
      # If md_dir already exists then check the already generated files
      already_generated_csv = os.listdir(md_dir)
      # Save the already generated files names
      already_generated_csv = [
          f.split(".")[0] for f in already_generated_csv
      ]
      # Possible directories in the original aishell1
      original_aishell1_dirs = ["dev", "test", "train"]
      # Actual directories extracted in your aishell1 version
      actual_aishell1_dirs = set(next(os.walk(aishell1_dir))[1]) & set(
          original_aishell1_dirs
      )
      # Actual directories that haven't already been processed
      not_already_processed_directories = list(
          set(actual_aishell1_dirs) - set(already_generated_csv)
      )
      return not_already_processed_directories
  
file_path: speechbrain/recipes/Aishell1Mix/separation/scripts/create_aishell1_metadata.py
imports: import os
  import argparse
  import soundfile
  import pandas
  import glob
  from tqdm import tqdm
label_desc: Use image node_id 4 for calling a global function with example usage: check_already_generated(md_dir, aishell1_dir) and returns: not_already_processed_directories