Graph.GmapGraph mapping. Map a graph to another one.
module type V_SRC = sig ... endSignature for the source graph.
module type V_DST = sig ... endSignature for the destination graph.
Provide a mapping function from a mapping of vertices.
module type E_SRC = sig ... endSignature for the source graph.
module type E_DST = sig ... endSignature for the destination graph.