proposition: Lemma CP_extensive (U : {set G}) : {subset U <= CP U}.
proof: Proof. Proof using. move => x inU. apply/bigcupP; exists (x,x); by rewrite ?inE /= ?inU // cpxx inE. Qed.
imports: mathcomp(all_ssreflect) GraphTheory(edone preliminaries digraph) GraphTheory(sgraph connectivity)