src/main/java/io/reactivex/internal/operators/observable/ObservableLastMaybe.java
@Override
    protected void subscribeActual(MaybeObserver<? super T> observer) {
        source.subscribe(new LastObserver<T>(observer));
    }
@Override
    protected void subscribeActual(MaybeObserver<? super T> observer) {
        source.subscribe(new LastObserver<T>(observer));
    }
@ Override protected void subscribeActual ( MaybeObserver < ? super T > observer ) { source . subscribe ( new LastObserver < T > ( observer ) ) ; }
TODO fuse back to Observable
TODO fuse back to Observable