Format code with black and isort

[c00kiemon5ter]

With this changeset the codebase is reformatted to be mostly pep8 compliant. The tools used are black and isort and their configurations are encoded in pyproject.toml as introduced by #872 .

This is the result after running the following commands that automatically reformat the code:

$ poetry run isort src/ tests/ example/
$ poetry run black src/ tests/ example/

and subsequently fixing some of the warning from

$ poetry run flake8 src/

PS: The intention is to make these part of a pre-commit hook and part of the CI checks.

All Submissions:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you added an explanation of what problem you are trying to solve with this PR?
• Have you added information on what your changes do and why you chose this as your solution?
• Have you written new tests for your changes?
• Does your submission pass tests?
• This project follows PEP8 style guide. Have you run your code against the 'flake8' linter?