∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.MonoidalCategory C] {f g h i j : C}
  (α : g ≅ h) (η : h ⟶ i) {ηs : i ⟶ j}
  {θ : CategoryTheory.MonoidalCategoryStruct.tensorObj f i ⟶ CategoryTheory.MonoidalCategoryStruct.tensorObj f j},
  CategoryTheory.MonoidalCategoryStruct.whiskerLeft f ηs = θ →
    CategoryTheory.MonoidalCategoryStruct.whiskerLeft f
        (CategoryTheory.CategoryStruct.comp α.hom (CategoryTheory.CategoryStruct.comp η ηs)) =
      CategoryTheory.CategoryStruct.comp (CategoryTheory.MonoidalCategory.whiskerLeftIso f α).hom
        (CategoryTheory.CategoryStruct.comp (CategoryTheory.MonoidalCategoryStruct.whiskerLeft f η) θ)