How do I get the FCM device registration_id

On the backend I’m using PyFCM and it requires the device registration_id.

How do I get that in Capacitor on Android? This tutorial, which works for sending the first test message, does not have the registration_id. I can send the first test message to all users of the app but I cannot yet get it to work with Python on the backend to message this specific app installation.
https://capacitor.ionicframework.com/docs/guides/push-notifications-firebase#android

To be clear, I’m asking for Capacitor support (not Python) needing to send the registration_id from Android to the backend, but this newbie doesn’t know how to obtain that token.