proposition: Lemma mem_cpring x : (x \in cpring) = cnode x0 x.
proof: Proof. by rewrite mem_rev -fconnect_orbit -!cnode1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)