proposition: Lemma subdom_umfiltk p f : {subset dom (um_filterk p f) <= p}.
proof: Proof. by move=>a; rewrite dom_umfiltk; case/andP. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)