public static Set GetSuccessors(Graph graph, Set point)
 {
     return graph.getSuccessors(point);
 } 
 public static List FindPath(Graph graph, Set from, Set to)
 {
     return graph.findPath(from, to);
 } 
 public static bool PathExists(Graph graph, Set from, Set to)
 {
     return (graph as HistoryGraph).findPath(from, to) != null;
 }