Refactor the code structure such that everything is in a more professional structure. Add and change the following things:

1. Make modules out of similar code
2. Pull appart files (like utils) and make multiple files with better common topics
3. Remove in-file if __name__ == "__main__" tests and add pytest tests
4. make package installable
5. Add CLI which can select train or visualize mode.
6. Add more modules to the YOLO model and make the code more readable
7. Fix PEP8 issues with flake8.