fact: Definition subgraph_succ2_D1 (m n : V) (gmn : g m n) : {set {set V}} := (fun n' => n' |: \bigcup_(m' in successors g n' :\ m) (subgraph g m' n')) @: (successors g m :\ n).
imports: mathcomp(all_ssreflect ssralg fingroup finalg perm zmodp) mathcomp(matrix) ssr_ext