PFAB #0 with step by step diff-breakdown

[baogianghoangvu]

PR for issue #1

Hi @robert! I've tried to incorporate a detailed diff breakdown into updated.py, from its original state all the way to your final, finished refactored version.

The idea was that I initialized the updated.py file as an exact copy of original.py, then I basically followed your recommendations section-by-section, named the commits accordingly (following your blogpost where possible).

This way I think would be helpful especially for "advanced beginners" who also might not be familiar yet with version control. Another plus is that the blogpost can directly link to relevant commits and readers can easily see the diffs between the original and refactored codes.

Thank you for the series and sorry for the late PR!