∀ {R : Type u_1} [inst : CommRing R] (X Y : CommAlgCat R),
  CommAlgCat.ofHom
      (Algebra.TensorProduct.map (CommAlgCat.Hom.hom (CategoryTheory.CategoryStruct.id X)) (AlgHom.id R ↑Y)) =
    CategoryTheory.CategoryStruct.id (CommAlgCat.of R (TensorProduct R ↑X ↑Y))