∀ {Ω : Type u_1} {ι : Type u_2} {_mΩ : MeasurableSpace Ω} {μ : MeasureTheory.Measure Ω} {β : Type u_10}
  {m : MeasurableSpace β} [inst : Mul β] [MeasurableMul₂ β] {f : ι → Ω → β},
  ProbabilityTheory.iIndepFun f μ →
    (∀ (i : ι), Measurable (f i)) →
      ∀ (i j k l : ι), i ≠ k → i ≠ l → j ≠ k → j ≠ l → ProbabilityTheory.IndepFun (f i * f j) (f k * f l) μ