Adding type annotations to project

[cpolish]

Hi,

First of all, thank you so much for making this fantastic project! It's really quite handy to generate pairs for thing such as testing.

As I'm a big fan of using type annotations in Python, I did notice that currently, the project doesn't use type annotations, which means that the types of various parameters/return values which are inferred via a type checker might appear as Unknown or Any.

Given that the project supports Python 3.7+, would there potentially be any interest in adding type annotation support, either directly in the source code, or via a .pyi stub file? If so, I'd be happy to contribute via a PR.

Thanks so much!

[thombashi]

@cpolish
Thank you for your suggestion.
I've considered adding type annotations to the package, but I have no time to do it.
Your pull request is welcome.
Embedding them directly into the source code would be preferable to using stub files.