I would like to preface this issue by saying that I really love this library, and use it a lot in my projects 😀

I personally see great importance in self-documenting code, and a large part of self-documenting code is being able to view
a function's arguments and their types in an IDE when using an API, without looking at its docs.
As this library has no official API reference (which is totally fine!), I think its crucial that the function signatures are clear to the user.

I see 2 choices for achieving this:

1. Adding a .pyi file. (this means that every change to Env's API means a change in the .pyi file too)
2. Rewrite Env's methods so that they have a clear signature that IDEs can parse.

I personally think the 1st option is easier, but wanted to know your opinion before submitting a PR.