I wouldn't recommend using this, based on the
first sentence in the README:
This code is deprecated and should not be used
Instead, see
this article for an informative walkthrough of the process. It includes python code and a few helpful tips to keep in mind. However, if you're planning on using these keys to store or manage significant sums of money, I would recommend using either a dedicated hardware wallet (like Trezor or the Ledger Nano X) or Bitcoin Core itself, built and run on a machine that has never been online (and ideally doesn't even have networking capabilities at all).