proposition: Lemma filternat_imply : isfilter_imply filternat.
proof: Proof. intros P Q H. apply hinhfun. intros N. exists (pr1 N). intros n Hn. now apply H, (pr2 N). Qed.
imports: UniMath.Foundations.Preamble UniMath.MoreFoundations.Tactics UniMath.Topology.Prelim UniMath.MoreFoundations.PartA