∀ {α : Type u_1} {β : Type u_2} {γ : Type u_3} {mα : MeasurableSpace α} {mβ : MeasurableSpace β}
  {mγ : MeasurableSpace γ} (κ : ProbabilityTheory.Kernel (α × β) γ) (a : β × α) (s : Set γ),
  (κ.swapLeft a) s = (κ a.swap) s