∀ {α : Type u_1} {β : Type u_2} {mα : MeasurableSpace α} {mβ : MeasurableSpace β} (κ : ProbabilityTheory.Kernel α β)
  [inst : ProbabilityTheory.IsSFiniteKernel κ] (f : α → β → NNReal),
  ProbabilityTheory.IsSFiniteKernel (κ.withDensity fun a b => ↑(f a b))