def train_test_split(windows, labels, size=.2):
    """
    Splits windows and labels into train and test splits.
    """
    
    split_size = int(len(windows) * (1-size))
    
    window_train = windows[:split_size]
    window_test = windows[split_size:]
    
    label_train = windows[:split_size]
    label_test = windows[split_size:]
    
    return window_train, window_test, label_train, label_test