∀ (C : Type u) [inst : CategoryTheory.Category.{v, u} C] {n : ℕ} (D : Type u_1)
  [inst_1 : CategoryTheory.Category.{v_1, u_1} D] (H : CategoryTheory.Functor C D)
  (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C) (X : (SimplexCategory.Truncated n)ᵒᵖ),
  (((CategoryTheory.SimplicialObject.Truncated.whiskering C D).obj H).obj F).obj X = H.obj (F.obj X)