How do you use MusicSubscription.Updates to detect changes?

Since I want to play music, I'd like to get notified when the user gets a valid apple music subscription. The way seems to be MusicSubscription.Updates but I can't figure out how to use it, and I can't find any code examples.

Can anyone point to a code example of how it works?

thanks

How do you use MusicSubscription.Updates to detect changes?
 
 
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