∀ {α : Type u_1} {β : Type u_2} {γ : Type u_3} {mα : MeasurableSpace α} {mβ : MeasurableSpace β}
  {mγ : MeasurableSpace γ} [inst : MeasurableSpace.CountablyGenerated γ] (κ : ProbabilityTheory.Kernel α (γ × β))
  [ProbabilityTheory.IsFiniteKernel κ] (a : α), ∀ᵐ (x : γ) ∂κ.fst a, κ.density κ.fst a x Set.univ = 1