Update black to version 20
Black is set to version "^19.10b0" on the pyproject.toml; however, it seems that `pre-commit` fetches the latest version, which is [20.8b1](https://github.com/psf/black/releases/tag/20.8b1).
As a consequence, black formatting is different while coding and on the pre-commit.
I suggest updating black.
issue