fact: Definition filterbase : (X → hProp) → hProp := λ A : X → hProp, (∃ B : X → hProp, base B × ∏ x, B x → A x).
imports: UniMath.Foundations.Preamble UniMath.MoreFoundations.Tactics UniMath.Topology.Prelim UniMath.MoreFoundations.PartA