val map : (G_Src.E.t -> G_Dst.edge) -> G_Src.t -> G_Dst.tval filter_map : (G_Src.E.t -> G_Dst.edge option) -> G_Src.t -> G_Dst.tGmap.Edgeval map : (G_Src.E.t -> G_Dst.edge) -> G_Src.t -> G_Dst.tval filter_map : (G_Src.E.t -> G_Dst.edge option) -> G_Src.t -> G_Dst.t