proposition: Lemma ecpR'_eq : ecpR' = node x0 :> G.
proof: Proof. by rewrite /ecpR' /ecpR /= -orderSpred /= subSnn. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)