∀ {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) [ProbabilityTheory.IsZeroOrMarkovKernel κ]
  (η : ProbabilityTheory.Kernel (α × β) γ) [ProbabilityTheory.IsZeroOrMarkovKernel η],
  ProbabilityTheory.IsZeroOrMarkovKernel (κ.compProd η)