∀ {α : Type u_1} {β : Type u_2} {f g : α → β} {mα : MeasurableSpace α} [inst : TopologicalSpace β] [inst_1 : Sub β]
  [ContinuousSub β],
  MeasureTheory.StronglyMeasurable f → MeasureTheory.StronglyMeasurable g → MeasureTheory.StronglyMeasurable (f - g)