∀ {X Y : AlgebraicGeometry.Scheme} (f : X ⟶ Y) {x : ↥X},
  CategoryTheory.CategoryStruct.comp (AlgebraicGeometry.Spec.map (AlgebraicGeometry.Scheme.Hom.stalkMap f x))
      (Y.fromSpecStalk (f x)) =
    CategoryTheory.CategoryStruct.comp (X.fromSpecStalk x) f