Apply `black` autoformatting suggestions

[aitorres]

What I did

I noticed that the black check that runs on Github Actions was not passing successfully on master. This PR just applies and commits all the suggested formatting changes, so that it starts passing again.

Nothing too groundbreaking ;-) No change is expected apart from the formatting changes.

You can verify that everything passes by running black --check . from the repo's root directory.

[EverettBerry]

Great stuff - all checks passed in the Actions!