∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] [inst_1 : CategoryTheory.Preadditive C]
  [inst_2 : CategoryTheory.Limits.HasZeroObject C] [inst_3 : CategoryTheory.HasShift C ℤ]
  [inst_4 : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] [inst_5 : CategoryTheory.Pretriangulated C]
  (t : CategoryTheory.Triangulated.TStructure C) (a b : ℤ) (h : a + 1 = b) (X : C) {Z : C}
  (h_1 : (t.truncGT a).obj X ⟶ Z),
  CategoryTheory.CategoryStruct.comp ((t.truncGEπ b).app X)
      (CategoryTheory.CategoryStruct.comp ((t.truncGTIsoTruncGE a b h).inv.app X) h_1) =
    CategoryTheory.CategoryStruct.comp ((t.truncGTπ a).app X) h_1