proposition: Lemma cubic_embr : quasicubic embr_ring.
proof: Proof. by have: cubic Gm := cexGm; rewrite (cubic_patch ppGm) => /andP[]. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color chromogram coloring patch) fourcolor(snip revsnip kempe birkhoff contract)