fact: Definition ex_filter_lim_base {T : TopologicalSpace} (F : Filter T) := ∃ (x : T) base, is_filter_lim_base F x base.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Topology.Filters UniMath.Algebra.Groups UniMath.Algebra.DivisionRig UniMath.Algebra.ConstructiveStructures