{C : Type u₁} →
  [inst : CategoryTheory.Category.{v₁, u₁} C] →
    {X Y : C} →
      {f : X ⟶ Y} →
        {motive : CategoryTheory.SplitMono f → Sort u} →
          (t : CategoryTheory.SplitMono f) →
            ((retraction : Y ⟶ X) →
                (id : CategoryTheory.CategoryStruct.comp f retraction = CategoryTheory.CategoryStruct.id X) →
                  motive { retraction := retraction, id := id }) →
              motive t