∀ {i j : CategoryTheory.Limits.WalkingParallelPairᵒᵖ} (f : i ⟶ j),
  CategoryTheory.CategoryStruct.comp
      ((CategoryTheory.Limits.walkingParallelPairOp.leftOp.comp CategoryTheory.Limits.walkingParallelPairOp).map f)
      ((fun j => CategoryTheory.eqToIso ⋯) j).hom =
    CategoryTheory.CategoryStruct.comp ((fun j => CategoryTheory.eqToIso ⋯) i).hom
      ((CategoryTheory.Functor.id CategoryTheory.Limits.WalkingParallelPairᵒᵖ).map f)