Module type MultiGraph.P
module type P =Interface for persistent implementations of labeled directed multi-graphs.sig..end
include MultiGraph.G
val empty : t
 The empty multi-graph.
val add_vertex : t -> Vertex.t -> tadd_vertex g v adds the vertex v to the multi-graph g.
 Precondition 
v is not already contained in g.val del_vertex : t -> Vertex.t -> tdel_vertex g v removes the vertex v from the multi-graph g.  All
 edges e with source E.src e or target E.tgt e equal to v are also
 removed from g.
 Precondition 
v is contained in g.val add_edge : t -> Edge.t -> tadd_edge g e adds the edge e to the multi-graph g.  The source
 E.src e and target E.tgt e vertices of e are also added to g if
 they are not already in g.
 Precondition 
e is not already contained in g.val del_edge : t -> Edge.t -> tdel_edge g e removes the edge e from the multi-graph g.
 Precondition 
e is contained in g.