##### Motivation for this change

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##### Checklist

- [ ] added corresponding entries in `CHANGELOG_UNRELEASED.md`

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<!-- consider using a temporary CHANGELOG_PR1234.md instead -->
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<!-- consider the use of `changelog/changes.sh` from
     https://github.com/math-comp/tools to generate the changelog -->

- [ ] added corresponding documentation in the headers

Reference: [How to document](https://github.com/math-comp/math-comp/wiki/How-to-document)

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##### Reminder to reviewers

- Read [this Checklist](https://github.com/math-comp/math-comp/wiki/Checklist-for-creating-and-review-PRs)
- Put a milestone if possible
- Check labels
