∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] {B A : C} {f : A ⟶ B} [inst_1 : CategoryTheory.Mono f]
  {X : CategoryTheory.Subobject B} (h : CategoryTheory.Subobject.mk f ≤ X),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Subobject.ofMkLE f X h) X.arrow = f