∀ {α : Type u_1} {β : Type u_2} {mα : MeasurableSpace α} {mβ : MeasurableSpace β}
  {κ : ProbabilityTheory.Kernel α (β × ℝ)} {ν : ProbabilityTheory.Kernel α β} {f : α × β → ℚ → ℝ},
  ProbabilityTheory.IsRatCondKernelCDF f κ ν →
    ∀ (a : α), ∀ᵐ (b : β) ∂ν a, Filter.Tendsto (f (a, b)) Filter.atBot (nhds 0)