Add custom id in firebase using ionic

Hi, i have a problem, i would like to add custom id (‘classification’) in my collection (‘pdpc’) but i seems lost.

this is my firebase.service.ts code.

export class FirebaseService {

private notes: Observable<Note>;

private noteCollection: AngularFirestoreCollection;

constructor(private afs: AngularFirestore) {

this.noteCollection = this.afs.collection<Note>('/pdpc/').doc('classification');

this.notes = this.noteCollection.snapshotChanges().pipe(

    map(actions => {

      return actions.map(a => {

        const data = a.payload.doc.data();

        const id = a.payload.doc.id;

        return { id, ...data };

      });

    })

);

}

getNotes(): Observable<Note> {

return this.notes;

}