It was good to re-establish the basics of Python object orientation, and I think I was able to complete the study safely because the type hinting part explained well about when it would be good to use elements in the typing module. As of now, Python has been released up to version 3.11, and while studying while reading the lecture and official documentation, I think that now, instead of importing the typing module, you can use built-in objects to express things like list[str], tuple[int], and in the case of Union and Optional types, you can use "|" like int|None. If you have time, it would be good if you could tell me more about these things. Thank you for the great lecture. :)