functor (G_Src : E_SRC) -> functor (G_Dst : E_DST) -> sig val map : (G_Src.E.t -> G_Dst.edge) -> G_Src.t -> G_Dst.t val filter_map : (G_Src.E.t -> G_Dst.edge option) -> G_Src.t -> G_Dst.t end