∀ {α : Type u_1} [inst : MeasurableSpace α] [inst_1 : MeasurableSpace.CountablyGenerated α] (n : ℕ)
  (m : MeasurableSpace ↑(MeasurableSpace.countablePartition α n)),
  Measurable fun a => ⟨MeasurableSpace.countablePartitionSet n a, ⋯⟩