I saw it in nostr:npub1tm99pgz2lth724jeld6gzz6zv48zy6xp4n9xu5uqrwvx9km54qaqkkxn72 code base.
https://github.com/0xchat-app/nostr-mls-package
But we have our own Nostr Models (sherd types) package and it might be more worthwhile to just integrate there. Will see.