class LinkkiInMemoryContainer extends com.vaadin.v7.data.util.AbstractInMemoryContainer<T, Object, com.vaadin.v7.data.Item> implements com.vaadin.v7.data.Container.Hierarchical {

    @Override
    public boolean hasChildren(Object itemId) {
        return getHierarchicalItem(itemId)
                .map(HierarchicalRowPmo::hasChildRows)
                .orElse(false);
    }

}