def METHOD_NAME(args):
    prefix_hash_set = set()
    train_file = path.join(args.notation_data_dir, "train.txt")
    with open(train_file) as f:
        for line in f:
            moves = line.strip().split()
            for i in range(len(moves)):
                prefix_hash_set.add(hash(tuple(moves[0: i + 1])))
    print(f"Unique train prefixes: {len(prefix_hash_set)}")
    return prefix_hash_set