∀ {X Y Z : AlgebraicGeometry.Scheme} {f : X ⟶ Y} {g : Y ⟶ Z} {x : ↥X} [AlgebraicGeometry.LocallyQuasiFinite g],
  AlgebraicGeometry.Scheme.Hom.QuasiFiniteAt (CategoryTheory.CategoryStruct.comp f g) x ↔
    AlgebraicGeometry.Scheme.Hom.QuasiFiniteAt f x