proposition: Lemma locally_base_and : isfilter_and (neighborhood' x base).
proof: Proof. intros A B Ha Hb. apply (pr2 (neighborhood_equiv _ _ _)). eapply neighborhood_and. - eapply neighborhood_equiv, Ha. - eapply neighborhood_equiv, Hb. Qed.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Topology.Filters UniMath.Algebra.Groups UniMath.Algebra.DivisionRig UniMath.Algebra.ConstructiveStructures