def test_equals(self):
     self.assertEqual(power([1, 2, 3]), [
         [], [1], [2], [3], [1, 2], [1, 3], [2, 3], [1, 2, 3]
     ])
 def test_equals_2(self):
     self.assertEqual(power([1, 2, 3, 4]), [
         [], [1], [2], [3], [4], [1, 2], [1, 3], [1, 4], [2, 3], [2, 4],
         [3, 4], [1, 2, 3], [1, 2, 4], [1, 3, 4], [2, 3, 4], [1, 2, 3, 4]
     ])