Upgrade to Python 3.9

[Hritik14]

As we have gone through some major changes in #525, we could also update the python version and carry on with the importer rewrites (#597) accordingly.

We could either upgrade to python 3.9 or python 3.10. This issues serves as a tracker for opinions.

[sify21]

which version does the project currently use? I tried with python 3.11.5 and encountered errors during pip install
https://stackoverflow.com/questions/74553366/yarl-quoting-c19612-fatal-error-longintrepr-h-file-not-found-1-error-ge