proposition: Lemma valid_umfiltUnL f1 f2 p : valid (f1 \+ f2) -> valid (um_filter p f1 \+ f2).
proof: Proof. move=>VH; case: validUn=>//; rewrite ?valid_umfilt ?(validL VH) ?(validR VH) //. by move=>k /dom_umfilt [v1][_ /In_dom] /(dom_inNL VH) /negbTE ->. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)