proposition: Lemma isaprop_isSetOfOpen_and : isaprop isSetOfOpen_and.
proof: Proof. apply impred_isaprop ; intros A. apply impred_isaprop ; intros B. apply isapropimpl, isapropimpl. now apply propproperty. Qed.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Topology.Filters UniMath.Algebra.Groups UniMath.Algebra.DivisionRig UniMath.Algebra.ConstructiveStructures