`include Builder.S`
`module G : Sig.G`
`val empty : unit -> G.t`
`val copy : G.t -> G.t`
`val add_vertex : G.t -> G.V.t -> G.t`
`val add_edge : G.t -> G.V.t -> G.V.t -> G.t`
`val add_edge_e : G.t -> G.E.t -> G.t`
`val remove_vertex : G.t -> G.V.t -> G.t`
`val remove_edge : G.t -> G.V.t -> G.V.t -> G.t`
`val remove_edge_e : G.t -> G.E.t -> G.t`
`val weight : G.edge -> weight`

Assign weights to edges.