proposition: Fact gcompr_subproof : cancel3 gcompr_edge gcompr_node gcompr_face.
proof: Proof. by move=> v; apply/val_inj/edgeK. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry jordan color coloring)