∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {X Y : C} (f g : X ⟶ Y)
  [inst_1 : CategoryTheory.Limits.HasEqualizer f g],
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.equalizerSubobjectIso f g).hom
      (CategoryTheory.Limits.equalizer.ι f g) =
    (CategoryTheory.Limits.equalizerSubobject f g).arrow