Clearly specified formatting rule

[jdossgollin]

The use of an automated tool (like black https://pypi.org/project/nb-black/ https://github.com/psf/black or similar) might help keep code formatted appropriately. There are GitHub actions that can do this automatically, and the nb-black extension will do it for jupyter notebooks. The current code does not have major formatting problems, but as more people start working together this may help to prevent syntax confusion.

[abpoll]

Updated coding environment to use black for src/ but not notebooks. nb-black doesn't install into the mamba environment I use. Will look into a formatting standard for notebooks.