ruff format/check

[clarasb]

This PR includes:

• Formatting changes from ruff format
• Fixes for issues reported by ruff check

Note: failing tests get fixed by PR #110.

---

Checklist (strike out non-applicable):

• Changes documented in CHANGES.md
• Related issue exists and is referred to in the PR description and CHANGES.md
• Added docstrings and API docs for any new/modified user-facing classes and functions
• Changes/features documented in docs/*
• Unit-tests adapted/added for changes/features
• Test coverage remains or increases (target 100%)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.92%. Comparing base (6dd4583) to head (3256d37).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #109   +/-   ##
=======================================
  Coverage   99.92%   99.92%           
=======================================
  Files          30       30           
  Lines        1414     1418    +4     
=======================================
+ Hits         1413     1417    +4     
  Misses          1        1           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.