def METHOD_NAME(url, md5sum, target_dir, manifest_path=None):
    """Download, unpack and create manifest file."""
    data_dir = os.path.join(target_dir, 'data_aishell')
    if not os.path.exists(data_dir):
        filepath = download(url, md5sum, target_dir)
        unpack(filepath, target_dir)
        # unpack all audio tar files
        audio_dir = os.path.join(data_dir, 'wav')
        for subfolder, _, filelist in sorted(os.walk(audio_dir)):
            for ftar in filelist:
                unpack(os.path.join(subfolder, ftar), subfolder, True)
    else:
        print("Skip downloading and unpacking. Data already exists in %s." %
              target_dir)
    if manifest_path:
        create_manifest(data_dir, manifest_path)