def test_append(self):
     A=[[1,2,3],[4,5,6]]
     B=[[1,2,3],[4,5,6]]
     expected_result=[[1, 2, 3, 1, 2, 3], [4, 5, 6, 4, 5, 6]]
     actual_result=Matrix.append(A, B)
     self.assertEqual(expected_result, actual_result)