proposition: Lemma omf_undef f : f um_undef = um_undef.
proof: Proof. by case: f=>s [m H] /=; rewrite H omap_undef. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)