proposition: Lemma omorph0 : f \bot = \bot.
proof: Proof. by rewrite -[\bot in LHS]set_join0 omorphSJ image_set0 set_join0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype choice order) mathcomp(ssrnat bigop classical_sets)