pub fn recursive_dfs_visit<G, C, V>(
    g: &G,
    from: <G as WithEdge>::OptionEdge,
    u: <G as WithVertex>::Vertex,
    color: &mut C,
    vis: &mut V
) -> Controlwhere
    G: Incidence,
    C: VertexPropMut<G, Color>,
    V: Visitor<G>,