Add type hints for the get_unused_code function and the fields of Item.

[johndoknjas]

Description

This PR adds type hints to make it slightly easier for users to use the api. Now for each element from get_unused_code, IDEs will display their type as Item when highlighting over the variable. The same is done for the fields of Item, such as making filename's type a Path (removing any potential confusion about whether it's a string).

Related Issue

Checklist:

• I have updated the documentation in the README.md file or my changes don't require an update.
• I have added an entry in CHANGELOG.md.
• I have added or adapted tests to cover my changes.
• I have run pre-commit run --all-files to format and lint my code.

[jendrikseipp]

Thanks for the PR! I'm a bit reluctant to merge it because type annotations without tests might get outdated quickly when the code changes. Is there a way to test that all type annotations are correct, while ignoring all other typing issues that a tool like Mypy might detect? Could you add such a test?

[johndoknjas]

@jendrikseipp For sure, I'll work on adding a test to do this.

[johndoknjas]

@jendrikseipp I've added a test that runs mypy, disabling error codes that mypy complains about at the moment. All of them seem like codes that in general shouldn't be needed to detect wrong type annotations.

By the way, before disabling the attr-defined error code, I noticed mypy called out lines 552 and 659 in core.py - not sure if it's right about these being issues.

[jendrikseipp]

Thanks, I'll have a closer look at this when time allows.

[johndoknjas]

Hey @jendrikseipp, just following up on this PR.

[jendrikseipp]

Thanks for your persistence :)

[jendrikseipp]

Suggested change

	sys.version_info >= (3, 13), reason="Need python < 3.13 for pytype"
	sys.version_info >= (3, 13), reason="needs Python < 3.13 for pytype"

[jendrikseipp]

Thanks for your work on this!

[johndoknjas]

No problem, and thank you for your feedback :)