Self-Diagnosis

• [ ] This pull request fixes #ISSUE_NUMBER.
• [ ] This pull request is related to SOME_REFERENCE.
• [ ] This pull request is small, uncontroversial, complete, and easy to review.
• [ ] I have enabled and run all GitHub Actions CI in my fork repository, and hence expect CI to be all-green for this pull request.
• [ ] I have read the contribution guidelines, and this pull request meets these guidelines for contribution.
• [x] I had trouble understanding parts of this questionnaire. (Please elaborate.)

Description

TODO: This pull request does X because of Y in order to Z.