∀ {R : Type u} [inst : CommSemiring R] {σ : Type u_1} {ι : Type u_2} {S : Type u_3} [inst_1 : CommSemiring S]
  [inst_2 : Algebra R S] (r : S), (MvPolynomial.tensorEquivSum R σ ι S) (MvPolynomial.C r ⊗ₜ[R] 1) = MvPolynomial.C r