∀ (Y : AlgebraicGeometry.Scheme) {X Y_1 Z : Y.IdealSheafDataᵒᵖ} (f : X ⟶ Y_1) (g : Y_1 ⟶ Z),
  CategoryTheory.Over.homMk (AlgebraicGeometry.Scheme.IdealSheafData.inclusion ⋯) ⋯ =
    CategoryTheory.CategoryStruct.comp
      (CategoryTheory.Over.homMk (AlgebraicGeometry.Scheme.IdealSheafData.inclusion ⋯) ⋯)
      (CategoryTheory.Over.homMk (AlgebraicGeometry.Scheme.IdealSheafData.inclusion ⋯) ⋯)