I've been away for quite some time (things came up, sorry) and am just getting back up to speed on the issues and PRs that have arisen. As preparation for other changes, this PR re-applies Black formatting and wraps docstrings at a more reasonable ~88 columns, matching Black's default line length.
It seems that CI is failing on master, but this PR doesn't change anything other than code formatting, so I'll probably end up merging it despite the CI failure, and then hopefully be able to fix CI next/soon. FWIW, tests at least seem to pass with 2.7.18 and 3.9.6 running locally on an M1 Mac - just that some of the other Python versions seem to fail in CI in tox's matrix testing.