public void forEachData(Consumer<T> action) {
        Objects.requireNonNull(action);
        action.accept(data());
        children.forEach(node -> node.forEachData(action));
    }
@author Nico Bergemann <barracuda415 at yahoo.de>
@param <T>
disunity-core/src/main/java/info/ata4/util/collection/Node.java