Better documentation around using different python versions for different modules

Documentation

As far as I can tell from the docs/google searches/looking through github issues, there isn't guidance on the standard or simplest ways to run mypy in a monorepo of sorts where different directories are on different python versions. I was hoping I could use the python_version config option, but it seems like that can only be set on a global level.

I guess one workaround would be replacing calls like mypy . with a series of calls running over specific directories with their specific python versions, but I was wondering if there is a less cumbersome approach.

既存の python_version 設定オプションに関するドキュメントとリファレンスを確認し、それらを issue で説明されている monorepo およびディレクトリ単位のユースケースと比較します。モジュール間で異なる Python バージョンを確認するための、標準的または最も簡単なサポート対象の方法を、必要なコマンド例または設定例とともにドキュメント化できれば完了です。