fact: Definition base_of_neighborhood {T : TopologicalSpace} (x : T) := ∑ (B : (T → hProp) → hProp), is_base_of_neighborhood x B.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Topology.Filters UniMath.Algebra.Groups UniMath.Algebra.DivisionRig UniMath.Algebra.ConstructiveStructures