∀ {σ : Type u_1} (R : Type u_2) [inst : CommSemiring R] (s : Set (σ →₀ ℕ)),
  IsUpperSet s →
    ∀ (x y : MvPolynomial σ R), y ∈ (MvPolynomial.restrictSupport R s).carrier → ∀ m ∈ (x * y).support, m ∈ s