### Mapping of vertices

`module type V_SRC = sig ... end`

Signature for the source graph.

`module type V_DST = sig ... end`

Signature for the destination graph.

`module Vertex (G_Src : V_SRC) (G_Dst : V_DST) : sig ... end`

Provide a mapping function from a mapping of vertices.

### Mapping of edges

`module type E_SRC = sig ... end`

Signature for the source graph.

`module type E_DST = sig ... end`

Signature for the destination graph.

`module Edge (G_Src : E_SRC) (G_Dst : E_DST) : sig ... end`

Provide a mapping function from a mapping of edges.