CompositeDomainObjectSet<T> out = new CompositeDomainObjectSet<T>(delegate, callbackActionDecorator);
        for (DomainObjectCollection<? extends T> c : collections) {
            out.addCollection(c);
        }
        return out;
    }

    private CompositeDomainObjectSet(DefaultDomainObjectSet<T> delegate, CollectionCallbackActionDecorator callbackActionDecorator) {
        super(delegate);