What push notification API does brave run?

I’m currently workin on java push notification system for a rest web app and
I was wondering which API does Brave use for sending push notifications to the browser? Is it Mozilla’s push service because of the MPL license, or since its Chromium base does it implement Firebase Cloud Messaging as Chrome?

Thank you

I can’t get push notification to work in Brave.
the getToken from Firebase,getToken never ends.
End using the push api I always get a request failed on
const subscription = await self.registration.pushManager.subscribe(options)
sw.js:1 Uncaught (in promise) TypeError: Request failed