∀ {C : Type u_2} {ι : Type u_3} [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.Abelian C]
  {c : ComplexShape ι} {S : CategoryTheory.ShortComplex (HomologicalComplex C c)} (i j : ι),
  CategoryTheory.Epi
    ((HomologicalComplex.HomologySequence.composableArrows₃ S.X₃ i j).map' 2 3
      HomologicalComplex.HomologySequence.instEpiMap'ComposableArrows₃OfNatNat._proof_2
      HomologicalComplex.HomologySequence.instEpiMap'ComposableArrows₃OfNatNat._proof_3)