Apply code formatting and linting tools

[sechkova]

Is your feature request related to a problem? Please describe.

The project lacks coding style guidelines.

Describe the solution you'd like

Pick a coding style guideline and apply code formatters and linters. This will greatly simplify reviewing and spotting bugs.

Describe alternatives you've considered

Among the popular tools in the python ecosystem are the code formatter black and the linter pylint. Many possibilities exist though.