∀ {B : Type u} [inst : CategoryTheory.Bicategory B] {a b c d : B} {f f' : a ⟶ b} (η : f ⟶ f') (g : b ⟶ c) (h : c ⟶ d),
  CategoryTheory.CategoryStruct.comp
      (CategoryTheory.Bicategory.whiskerRight (CategoryTheory.Bicategory.whiskerRight η g) h)
      (CategoryTheory.Bicategory.associator f' g h).hom =
    CategoryTheory.CategoryStruct.comp (CategoryTheory.Bicategory.associator f g h).hom
      (CategoryTheory.Bicategory.whiskerRight η (CategoryTheory.CategoryStruct.comp g h))