MAINT: Static check on python files

For better maintainability, it's best practice to follow some python guidelines like PEP8 Ideally, you would want to have the following checks in CI pipeline:

1. black formatting: It automatically formats code, following PEP8 guidelines
2. flake8 formatting check: checks for some other PEP8 violations not corrected by black
3. isort check: checks formatting of import lines in python code
4. mypy check: checks types of all variables and arguments