Code doesn't work in more-python-for-beginners/01-Formatting and Linting

I've tried good.py both by python2 and python3, but it didn't work. Also, I've failed to understand why these codes are examples for formatting.... I've searched on google about formatting but it was about formatting strings in operators, braces or f-strings, which are not quite related to these codes.

I've found out the reason - there were indentation problems in good.py file, using space mixed with tap.