proposition: Lemma embddN : {morph embdd: u / node u}.
proof: Proof. by move=> u; rewrite /embdd /= (embedN (valP u)). 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)