@Override
    public List<T_TREE_NODE> getChildrenList(final T_TREE_NODE node) {
        final List<T_TREE_NODE> result = childrenMap.get(node);
        return result == null
                ? getEmptyList()
                : result;
    }
Creates a new instance with a given node as the root

@param root the node to be used as the root.
stroom-core-client-widget/src/main/java/stroom/widget/htree/client/treelayout/util/DefaultTreeForTreeLayout.java