/// @}

   template <typename _Graph>

   class GraphNodeSet {

   public:

     typedef _Graph Graph;

     typedef typename Graph::Node Item;

     typedef typename Graph::NodeIt ItemIt;

     template <typename _Value>

     class Map : public Graph::template NodeMap<_Value> {

     public:

       typedef typename Graph::template NodeMap<_Value> Parent; 

       typedef typename Parent::Value Value;

       Map(const Graph& _graph) : Parent(_graph) {}

       Map(const Graph& _graph, const Value& _value) 

 	: Parent(_graph, _value) {}

     };

     typedef IdMap<Graph, Item> IdMap;

   private:

     Graph* graph;

   };

   template <typename _Graph>

   class GraphEdgeSet {

   public:

     typedef _Graph Graph;

     typedef typename Graph::Edge Item;

     typedef typename Graph::EdgeIt ItemIt;

     template <typename _Value>

     class Map : public Graph::template EdgeMap<_Value> {

     public:

       typedef typename Graph::template EdgeMap<_Value> Parent; 

       typedef typename Parent::Value Value;

       Map(const Graph& _graph) : Parent(_graph) {}

       Map(const Graph& _graph, const Value& _value) 

 	: Parent(_graph, _value) {}

     };

     typedef IdMap<Graph, Item> IdMap;

   private:

     Graph* graph;

   };

   /// @}