Vehicle_magnetometer, who writes and reads?

As far as i can understand and i can see from the logs vehicle_magnetometer is a topic as others but i can’t see it in:uORB Publication/Subscription Graph | PX4 Guide (main)

Neither in the documentation uorb message reference where it links to a page not found.uORB Message Reference | Master (English) | PX4 User Guide

Am i missing or misunderstanding something? can someone link some documentation reporting exactly who reads and publish?