∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.Regular C] {X Y : C}
  (f : X ⟶ Y),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pullback.fst f f) f =
    CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pullback.snd f f) f