proposition: Lemma isaprop_isfilter_imply : isaprop isfilter_imply.
proof: Proof. apply impred_isaprop ; intro A. apply impred_isaprop ; intro B. apply isapropimpl. apply isapropimpl. apply propproperty. Qed.
imports: UniMath.Foundations.Preamble UniMath.MoreFoundations.Tactics UniMath.Topology.Prelim UniMath.MoreFoundations.PartA