Please enter a concise description of the changes proposed in the pull request,
along with any relevant links to external discussions.

-  If your pull request involves fixing a bug, then the relevant code
   should be in a branch that is a derivative of `master`, and you should
   select `master` as the target branch in the pull request; for all other
   pull requests, the relevant code should be in a branch that is a
   derivative of `dev`, and you should select `dev` as the target branch
   of the pull request (assuming no other more appropriate branch exists).

-  If your proposed changes address an [existing Issue](https://github.com/MRtrix3/mrtrix3/issues)
   listed on GitHub, please add a reference to that Issue (a "`#`"
   character followed by the issue number).

-  If your proposed changes are not yet ready to be merged, but you are
   creating a pull request in order to initiate communications on such,
   please flag it as a [draft pull request](https://github.blog/2019-02-14-introducing-draft-pull-requests/).

-  You may optionally add `@mentions` of a person or team appropriate
   for reviewing proposed changes.
