∀ {α : Type u_1} {β : Type u_2} {ι : Type u_4} [Countable ι] [inst : TopologicalSpace β] {m₀ : MeasurableSpace α}
  {μ : MeasureTheory.Measure α} {f : α → β} [TopologicalSpace.PseudoMetrizableSpace β] {s : ι → Set α},
  (∀ (i : ι), MeasureTheory.AEStronglyMeasurable f (μ.restrict (s i))) →
    MeasureTheory.AEStronglyMeasurable f (μ.restrict (⋃ i, s i))