∀ {α : Type u_1} {δ : Type u_4} [inst : TopologicalSpace α] {mα : MeasurableSpace α} [BorelSpace α]
  {mδ : MeasurableSpace δ} [inst_2 : ConditionallyCompleteLinearOrder α] [OrderTopology α] [SecondCountableTopology α]
  {ι : Type u_5} (s : Set ι) {f : ι → δ → α},
  s.Countable → (∀ i ∈ s, Measurable (f i)) → Measurable fun b => ⨆ i ∈ s, f i b