code: function (graph, head, where) {
      var routes = [];
  
      Graph.Visitor.Stacked(graph, head, function (node, stack, weight) {
        if (where && where.length !== stack.length){
          return;
        }
        routes.push(new Graph.Route(stack.slice(), weight));
      });
      return routes;
    }
docs: Helper that will return all the routes
  that have the given head node as
  a starting point.