proposition: Lemma kfilter_predI p1 p2 (s : fmap) : kfilter (predI p1 p2) s = kfilter p1 (kfilter p2 s).
proof: Proof. by apply/fmapE; rewrite /= /kfilter' filter_predI. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path) pcm(options)