def test_mean_square_error(self):
self.assertEqual(a1.mean_square_error(3, 4), 0.5)
self.assertEqual(a1.mean_square_error(3.5, 4), 0.125)
self.assertEqual(a1.mean_square_error(-3.5, -3.5), 0)
self.assertEqual(a1.mean_square_error(3.5, -3.5), 24.5)
