proposition: Lemma scycle_rev_ring : scycle rlink (rev_ring r).
proof: Proof. by rewrite /scycle cycle_rev_ring simple_rev_ring. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry patch sew snip color chromogram) fourcolor(coloring kempe)