def make_train_test_splits(windows, labels, test_split=0.2):
    """
    Splits matching pairs of windows and labels into train and test splits.
    """
    split_size = int(len(windows) * (1-test_split)) # this will default to 80% train/20% test
    train_windows = windows[:split_size]
    train_labels = labels[:split_size]
    test_windows = windows[split_size:]
    test_labels = labels[split_size:]
    return train_windows, test_windows, train_labels, test_labels