def METHOD_NAME():
    train_audio_files = os.listdir(train_audio_folder)
    dev_split = set()
    # randomly split the training set of 40 hours to 37 train and 3 dev
    dur = 7200
    while dur >= 0:
        f = random.choice(train_audio_files)
        while f in dev_split:
            f = random.choice(train_audio_files)
        wav_file = os.path.join(train_audio_folder, f)
        dev_split.add(f)
        dur -= get_duration(wav_file)
    return dev_split