Merge.IExtension for the module G.
Same specification than module type S but modify the graph inplace instead of returning a new graph.
type graph = G.ttype vertex = G.vertextype edge = G.edgetype edge_label = G.E.labelval merge_edges_with_label : ?src:vertex -> ?dst:vertex -> ?label:edge_label -> graph -> edge_label -> unitval merge_isolabelled_edges : graph -> unit