private DigraphProvider<? super DigraphLayoutNode<V>, Digraph<? extends DigraphLayoutNode<V>, ? extends DigraphLayoutArc<V, E>>> getSubgraphProvider() {
		return new DigraphProvider<DigraphLayoutNode<V>, Digraph<? extends DigraphLayoutNode<V>,? extends DigraphLayoutArc<V,E>>>() {
			@Override
			public Digraph<? extends DigraphLayoutNode<V>, ? extends DigraphLayoutArc<V, E>> get(DigraphLayoutNode<V> node) {
				LayoutTree<V, E> subtree = layoutTree.find(node.getVertex());
				return subtree == null ? null : subtree.getLayout().getLayoutGraph();
			}
		};
	}