∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Abelian C] {D : Type u'}
  [inst_2 : CategoryTheory.Category.{v', u'} D] [inst_3 : CategoryTheory.Abelian D] (F : CategoryTheory.Functor C D)
  [inst_4 : F.Additive] [inst_5 : CategoryTheory.Limits.PreservesFiniteLimits F]
  [inst_6 : CategoryTheory.Limits.PreservesFiniteColimits F] [inst_7 : CategoryTheory.HasExt C]
  [inst_8 : CategoryTheory.HasExt D] (X Y : C) (n : ℕ),
  ⇑(F.mapExtAddHom X Y n) = CategoryTheory.Abelian.Ext.mapExactFunctor F