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