∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.Preadditive C]
  (P Q : CategoryTheory.Idempotents.Karoubi C),
  CategoryTheory.CategoryStruct.comp P.p (CategoryTheory.CategoryStruct.comp 0 Q.p) = 0