> what if you change the implementation language later?

I don't think that is a thing that happens in real life.

* Practically, one package is associated with exactly one github repository, sometimes a few. You would see implementation switching from JavaScript to TypeScript, but almost never from python to Go. Normally people start a brand new project for that kind of thing. * The reality is that each language has its own library ecosystem, and people reinvent the wheel at least once for each language. I wish we live in a world where you could save the effort, instead implement everything only once and it runs efficiently and has idiomatic APIs everywhere. But that's not how it works. If you create a package for a language, that's it. You could reimplement the same thing like by line in another language, but that would be a different package for that language.