∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] [inst_1 : CategoryTheory.Abelian C]
  {S₁ S₂ : CategoryTheory.ShortComplex.SnakeInput C} (self : S₁.Hom S₂),
  CategoryTheory.CategoryStruct.comp self.f₂ S₂.v₂₃ = CategoryTheory.CategoryStruct.comp S₁.v₂₃ self.f₃