∀ {α : Type u_1} {β : Type u_2} {γ : Type u_3} [inst : MeasurableSpace α] [inst_1 : MeasurableSpace β]
  [inst_2 : MeasurableSpace γ] {μ : MeasureTheory.Measure α} {ν : MeasureTheory.Measure β} {f : α → γ} {g : β → γ},
  ProbabilityTheory.IdentDistrib f g μ ν → ∀ {s : Set γ}, MeasurableSet s → μ (f ⁻¹' s) = ν (g ⁻¹' s)