∀ {C : Type u_1} {D : Type u_2} [inst : CategoryTheory.Category.{v_1, u_1} C]
  [inst_1 : CategoryTheory.Category.{v_2, u_2} D] (F : CategoryTheory.Functor C D)
  [inst_2 : CategoryTheory.Limits.HasZeroMorphisms C] [inst_3 : CategoryTheory.Limits.HasZeroMorphisms D]
  [inst_4 : F.PreservesZeroMorphisms] (X : CochainComplex.Plus C) (x : ℤ),
  (F.mapCochainComplexPlusCompι.hom.app X).f x = CategoryTheory.CategoryStruct.id (F.obj (X.obj.X x))