∀ {X Y : AlgebraicGeometry.Scheme} {f g : X ⟶ Y},
  f = g →
    ∀ [inst : AlgebraicGeometry.IsOpenImmersion f] [inst_1 : AlgebraicGeometry.IsOpenImmersion g] (x : X.Opens),
      (AlgebraicGeometry.Scheme.Hom.opensFunctor g).obj x = (AlgebraicGeometry.Scheme.Hom.opensFunctor f).obj x