proposition: Lemma valid_umfiltUn p1 p2 f1 f2 : valid (f1 \+ f2) -> valid (um_filter p1 f1 \+ um_filter p2 f2).
proof: Proof. by move=>W; apply: valid_umfiltUnL (valid_umfiltUnR _ W). Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)