proposition: Lemma dom_umfilt_subset p f : {subset dom (um_filter p f) <= dom f}.
proof: Proof. by rewrite /um_filter; apply: dom_omap_sub. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)