∀ {α : Type u_1} {β : Type u_2} {γ : Type u_3} {mα : MeasurableSpace α} {mβ : MeasurableSpace β}
  {mγ : MeasurableSpace γ} {ι : Type u_5} [inst : Countable ι] {κ : ι → ProbabilityTheory.Kernel α β},
  (ProbabilityTheory.Kernel.sum fun i => ProbabilityTheory.Kernel.prodMkRight γ (κ i)) =
    ProbabilityTheory.Kernel.prodMkRight γ (ProbabilityTheory.Kernel.sum κ)