The HKSourceQuery provides a way for you to request what apps and devices are saving a specified sample type to the health store. This tutorial will be one of the shorter ones as there isn’t too much that can be done with this particular query.
A read through of the documentation shows that the HKSourceQuery simply has an init method, and nothing else.
samplePredicate objectPredicate: NSPredicate?,
completionHandler: @escaping (HKSourceQuery, Set<HKSource>?, Error?) -> Void)