Problems to update using Firebase inside a callback function

Hi guys,

I am trying to get and save an user TokenID that FCM (Firebase Cloud Messaging) provides to me when an user authenticates in my app in my Firebase database. The problem i have is that in setToken(), Ionic is not recognizing functions that i created to work with firebase database.

My home.ts code is here:![FB_IMG_1508845133145|690x128]

The error returned.

My objective is just obtain TokenID from FCM and store this info in Firebase.