def test_get_possible_values(self):
row = [1, 2, 3, None, None, None, 7, None, 9]
column = [None, None, None, None, 1, 2, 3, None, 8]
square = [None, None, None, None, None, None, None, None, 6]
self.assertListEqual([4, 5],Cell.get_possible_values(row, column, square))
