`black`en the code base

[KOLANICH]

The simplest way to satisfy various code style linters is to apply automatic reformatters. But now because the code base doesn't follow conventions of black I have to revert some changes by it. It is proposed to apply autopep8 -aaaa --experimental --max-line-length=110 -ir ., isort and black -l 110 (in this order!) to the code base in order to make the lives of contributors a bit easier.