proposition: Lemma umall2_refl f : Reflexive P -> um_all2 f f.
proof: Proof. by move=>R k; apply: Reflexive_optionR. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)