def test__mul__matrix(self) -> None:
        a = Matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]], 3, 3)
        x = Vector([1, 2, 3])
        self.assertEqual("(14,32,50)", str(a * x))
        self.assertEqual("|2,4,6|\n|8,10,12|\n|14,16,18|\n", str(a * 2))