∀ {R : Type t} [inst : Ring R] {C : Type u} [inst_1 : CategoryTheory.Category.{v, u} C]
  [inst_2 : CategoryTheory.Abelian C] [inst_3 : CategoryTheory.Linear R C] [inst_4 : CategoryTheory.HasExt C] {X Y : C}
  {n : ℕ} [inst_5 : HasDerivedCategory C]
  (a :
    CategoryTheory.ShiftedHom ((DerivedCategory.singleFunctor C 0).obj X) ((DerivedCategory.singleFunctor C 0).obj Y)
      ↑n),
  CategoryTheory.Abelian.Ext.homLinearEquiv.symm a = CategoryTheory.Abelian.Ext.homAddEquiv.invFun a