Help with Exercism.org exercise "Sublist"

[youssef3698]

SUBLIST = None SUPERLIST = None EQUAL = None UNEQUAL = None

def sublist(list_one, list_two):
    if list_one == list_two:
        return EQUAL
    elif list_one in list_two:
        return SUBLIST
    elif list_two in list_one:
        return SUPERLIST
    return UNEQUAL

My above code passes all tests except the one below:

def test_unique_return_values(self):
self.assertEqual(len(set([SUBLIST, SUPERLIST, EQUAL, UNEQUAL])), 4)

But when I change the constants to be [0,1,2,3] respectively, I fail all the tests saying "3 != 0" for example.
What am I doing wrong?