As written, I believe `P1_sq` and `P2_sq` are equivalent. In line 177 the first `[::-1]` reverse indexes the array, and the second restores it after squaring. Either the code isn't quite what you want, or this comment doesn't describe the behavior. 

When I run this I get `True`:

```python
>>> test1 = np.arange(27) ** 2
>>> test2 = (np.arange(27)[::-1] ** 2)[::-1]
>>> (test1 == test2).all()
True
```