public static void SetTentativeDistance(this CalculateShortestPath.DistanceGraphRole distanceGraph, int distance)
        {
            var context = Context.Current <CalculateShortestPath>();

            context.TentativeDistance[(Node)distanceGraph] = distance;
        }
        public static int TentativeDistance(this CalculateShortestPath.DistanceGraphRole distanceGraph)
        {
            var context = Context.Current <CalculateShortestPath>();

            return(context.TentativeDistance[(Node)distanceGraph]);
        }