I see the following code in `QuickGraph.Graphviz.GraphvizAlgorithm.Generate` which defines the `id` used for each vertex: ```csharp int i = 0; foreach (TVertex v in this.VisitedGraph.Vertices) this.vertexIds.Add(v, i++); ``` It would be nice to be able to override the default 1, 2, 3, n to maybe something defined in `TVertex`.