/// A wrapper for getting an undirected graph by forgetting

   /// A wrapper for getting an undirected graph by forgetting

   /// the orientation of a directed one.

   /// the orientation of a directed one.

   template<typename Graph>

   template<typename Graph>

   class UndirGraphWrapper : public GraphWrapper<Graph> {

   class UndirGraphWrapper : public GraphWrapper<Graph> {

   protected:

   protected:

   public:

   public:

     typedef typename GraphWrapper<Graph>::Node Node;

     typedef typename GraphWrapper<Graph>::Node Node;

     typedef typename GraphWrapper<Graph>::NodeIt NodeIt;

     typedef typename GraphWrapper<Graph>::NodeIt NodeIt;

     typedef typename GraphWrapper<Graph>::Edge Edge;

     typedef typename GraphWrapper<Graph>::Edge Edge;