∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {J : CategoryTheory.Limits.MultispanShape}
  (I : CategoryTheory.Limits.MultispanIndex J C) [inst_1 : CategoryTheory.Limits.HasCoproduct I.left]
  [inst_2 : CategoryTheory.Limits.HasCoproduct I.right] (b : J.L) {Z : C} (h : ∐ I.right ⟶ Z),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.Sigma.ι I.left b)
      (CategoryTheory.CategoryStruct.comp I.fstSigmaMap h) =
    CategoryTheory.CategoryStruct.comp (I.fst b)
      (CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.Sigma.ι I.right (J.fst b)) h)