proposition: Lemma codom_snipd : codom snipd =i diskN.
proof: Proof. move=> z; apply/imageP/idP => [[[y dNy] /= _ -> //] | dNz]. by exists (sub z dNz). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap jordan color geometry patch)