∀ {α : Type u_1} {β : Type u_2} {mα : MeasurableSpace α} {mβ : MeasurableSpace β} {μ : MeasureTheory.Measure α}
  {f : α → β}, AEMeasurable f μ → ∀ {s : Set β}, (MeasureTheory.Measure.map f μ) s = 0 → μ (f ⁻¹' s) = 0