∀ {Ω : Type u_1} {ι : Type u_3} {m : MeasurableSpace Ω} [inst : LinearOrder ι] {f : MeasureTheory.Filtration ι m}
  {τ : Ω → WithTop ι} (hτ : MeasureTheory.IsStoppingTime f τ),
  (Set.range τ).Countable → ∀ (i : ι), MeasurableSet {ω | τ ω < ↑i}