∀ {X : AlgebraicGeometry.Scheme} {U : X.Opens} (f g : ↑(X.presheaf.obj (Opposite.op U))) (𝒰 : X.OpenCover),
  (∀ (i : 𝒰.I₀),
      (CategoryTheory.ConcreteCategory.hom (AlgebraicGeometry.Scheme.Hom.app (𝒰.f i) U)) f =
        (CategoryTheory.ConcreteCategory.hom (AlgebraicGeometry.Scheme.Hom.app (𝒰.f i) U)) g) →
    f = g