proposition: Lemma omap0 a : omap a Unit = Unit.
proof: Proof. by rewrite /omap valid_unit assocs0. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)