human
Solve the following python programming problem given the following code:
def mnist() : 
    base_url = 'http://yann.lecun.com/exdb/mnist/' 
    def parse_labels(filename) : 
        with gzip.open (filename, 'rb') as fh : 
            (magic, num_data) = struct.unpack ('>II', fh.read (8)) 
            return np.array (array.array ('B', fh.read ()), dtype = np.uint8) 
def parse_images(filename) : 
        with gzip.open (filename, 'rb') as fh : 
            (magic, num_data, rows, cols) = struct.unpack ('>IIII', fh.read (16)) 
            return np.array (array.array ('B', fh.read ()), dtype = np.uint8).reshape (num_data, rows, cols) 
for filename in ['train-images-idx3-ubyte.gz', 'train-labels-idx1-ubyte.gz', 't10k-images-idx3-ubyte.gz', 't10k-labels-idx1-ubyte.gz'] : 
        download ((base_url + filename), filename) 
train_images = parse_images ('data/train-images-idx3-ubyte.gz') 
    train_labels = parse_labels ('data/train-labels-idx1-ubyte.gz') 
    test_images = parse_images ('data/t10k-images-idx3-ubyte.gz') 
    test_labels = parse_labels ('data/t10k-labels-idx1-ubyte.gz') 
    return (train_images, train_labels, base_url, test_labels) 

    
    

    Fix the buggy line: return (train_images, train_labels, base_url, test_labels)
assistant
#Here is Python program to fix the buggy line: return (train_images, train_labels, base_url, test_labels)
.

return (train_images, train_labels, test_images, test_labels)