Lemma isaprop_isfilter_notempty : isaprop isfilter_notempty. Proof. apply impred_isaprop ; intro A. apply isapropimpl. apply propproperty. Qed.
Require Import UniMath.Foundations.Preamble. Require Import UniMath.MoreFoundations.Tactics. Require Import UniMath.MoreFoundations.PartA.