Feat:Add mypy config and fix all errors

### Describe the feature

After contributing to few python libraries one thing I noticed their was they have mypy configs so I think it will be great if we add mypy configs to backend for better type hinting, reducing redundant expressions increasing the overall code quality.
I am willing to work on this

### Add ScreenShots

Currently backend has around 171 mypy errors:

### Record

- [x] I agree to follow this project's Code of Conduct
- [x] I want to work on this issue