add comments in R3BMusliMapped2Cal

[audreychatillon]

clang-format

Describe your proposal.

Mention any issue this PR is resolved or is related to.

---

Checklist:

• [ ] Rebased against dev branch
• [ ] My name is in the resp. CONTRIBUTORS/AUTHORS file
• [ ] Followed the pull request guidlines and the Git workflow
• [ ] Followed the seven rules of great commit messages