proposition: Lemma plane_emb_plain : plain (emb_map g).
proof: Proof. exact: emb_plain. Qed.
imports: mathcomp(all_ssreflect) fourcolor(hypermap geometry color coloring walkup combinatorial4ct cfmap) GraphTheory(edone preliminaries bij digraph sgraph) GraphTheory(connectivity minor hmap_ops smerge hcycle arc)