proposition: Fact gcompd_subproof : cancel3 gcompd_edge gcompd_node gcompd_face.
proof: Proof. by move=> u; apply/val_inj/edgeK. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry jordan color coloring)