Improve type hint

[hydra-zim]

I found that the return type of get_or_404 is Any now. This PR will bound return type to bond to Self

Checklist:

• [ ] Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• [ ] Add or update relevant docs, in the docs folder and in code.
• [ ] Add an entry in CHANGES.rst summarizing the change and linking to the issue.
• [ ] Add .. versionchanged:: entries in any relevant code docs.
• [x] Run pre-commit hooks and fix any issues.
• [x] Run pytest and tox, no tests failed.

[pamelafox]

@hydra-zim Is this ready for review? I notice you haven't completed the tasks on the checklist, like updating the changelog. Please go through those.