proposition: Lemma quasicubic_eq : quasicubic -> forall x, x \notin r -> node (node (node x)) = x.
proof: Proof. by move/cubicP=> cubicG x /cubicG[]. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap jordan)