code: public final Collection<Address> handleView(View newView) {
          View oldView;
          synchronized (deliverySet) {
              oldView = getAndSetView(newView);
              deliverySet.removeIf(this::removeMessage);
              notifyIfNeeded();
          }
          return View.leftMembers(oldView, newView);
      }
docs: Updates the current view in use and returns a {@link Collection} with the members that left the cluster.