∀ {σ : Type u_1} {R : Type u_3} {S : Type u_4} {T : Type u_5} [inst : CommSemiring R] [inst_1 : CommSemiring S]
  [inst_2 : CommSemiring T] (f : R →+* MvPolynomial σ S) (g : S →+* T) (φ : MvPolynomial σ R),
  (MvPolynomial.map g) ((MvPolynomial.bind₂ f) φ) = (MvPolynomial.bind₂ ((MvPolynomial.map g).comp f)) φ