Java Flow.Subscriber - How can I get the publisher of onComplete?

Question

I'm creating an user event system using JDK 9 Flow API, so I have a room (which extends the UserSubscriver class above), it may have many users and each user can offer (dispatch) updates at any time.

public abstract class UserSubscriver implements Flow.Subscriber<Notification> {
    private Flow.Subscription subscription;

    @Override
    public void onSubscribe(final Flow.Subscription subscription) {
        this.subscription = subscription;
        subscription.request(1);
    }

    @Override
    public void onError(final Throwable throwable) {
        // ...
    }

    @Override
    public void onNext(final Notification notification) {
        // ...
        subscription.request(1);
    }

    @Override
    public void onComplete() {
        // How can I know who was the publisher of this?
    }
}

User class:

public class User extends SubmissionPublisher<Notification> {

    ....

    public int offer(Notification item) {
        return super.offer(item, (sub, msg) -> false);
    }
}

On the onUpdate I can receive any args, so I can receive the publisher of the update, but there are no args on onComplete.

How can I know who was the publisher of an onComplete event?