∀ {X Y Z : SemiNormedGrp} {f : X ⟶ Y} {g : Y ⟶ Z} (w : CategoryTheory.CategoryStruct.comp f g = 0),
  CategoryTheory.CategoryStruct.comp (SemiNormedGrp.explicitCokernelIso f).hom
      (CategoryTheory.Limits.cokernel.desc f g w) =
    SemiNormedGrp.explicitCokernelDesc w