Update signatures of loads and parse to include return types

[jonathandung]

Fixes #107.

[dpranke]

Thanks for the fix! I admit I'm a bit surprised that I hadn't already done (or caught this), so it's appreciated.

One thing, though: the package still supports 3.9, so I don't think you can use | to indicate a union type (you can see the failure in this test run . Can you change line 225 to Union[tuple[...], tuple[...]]?

[jonathandung]

Sure. Done

[dpranke]

Argh, sorry, that needs to be typing.Tuple (or just Tuple) instead of tuple, for 3.8. I can change that for you in a separate commit, if you'd prefer?

[jonathandung]

I'll do it myself

[jonathandung]

While I'm at it, should I type the helper functions as well? (_convert and such)

[dpranke]

Sure, feel free to add types to anything in lib.py that is missing them.