template <typename _Base>

   class AlterableUndirBipartiteGraphExtender : public _Base {

   public:

     typedef _Base Parent;

     typedef AlterableUndirBipartiteGraphExtender Graph;

     typedef typename Parent::Node Node;

     typedef typename Parent::LowerNode LowerNode;

     typedef typename Parent::UpperNode UpperNode;

     typedef typename Parent::Edge Edge;

     typedef typename Parent::UndirEdge UndirEdge;

     typedef AlterationNotifier<Node> NodeNotifier;

     typedef AlterationNotifier<LowerNode> LowerNodeNotifier;

     typedef AlterationNotifier<UpperNode> UpperNodeNotifier;

     typedef AlterationNotifier<Edge> EdgeNotifier;

     typedef AlterationNotifier<UndirEdge> UndirEdgeNotifier;

   protected:

     mutable NodeNotifier nodeNotifier;

     mutable LowerNodeNotifier lowerNodeNotifier;

     mutable UpperNodeNotifier upperNodeNotifier;

     mutable EdgeNotifier edgeNotifier;

     mutable UndirEdgeNotifier undirEdgeNotifier;

   public:

     NodeNotifier& getNotifier(Node) const {

       return nodeNotifier;

     }

     LowerNodeNotifier& getNotifier(LowerNode) const {

       return lowerNodeNotifier;

     }

     UpperNodeNotifier& getNotifier(UpperNode) const {

       return upperNodeNotifier;

     }

     EdgeNotifier& getNotifier(Edge) const {

       return edgeNotifier;

     }

     UndirEdgeNotifier& getNotifier(UndirEdge) const {

       return undirEdgeNotifier;

     }

     ~AlterableUndirBipartiteGraphExtender() {

       nodeNotifier.clear();

       lowerNodeNotifier.clear();

       upperNodeNotifier.clear();

       edgeNotifier.clear();

       undirEdgeNotifier.clear();

     }

   };