public static Android.Gms.Tasks.Task UnsubscribeFromTopic(this FirebaseMessaging fb, string platform, YawsNotification.Topic topic)
{
#if DEBUG
var fbTopic = $"Debug-{platform}-{topic}";
#else
var fbTopic = $"{platform}-{topic}";
#endif
return(fb.UnsubscribeFromTopic(fbTopic));
}