∀ {X Y : SSet} {A : X.Subcomplex} {B : Y.Subcomplex} {φ : A.toSSet ⟶ B.toSSet} (f : SSet.RelativeMorphism A B φ),
  CategoryTheory.CategoryStruct.comp SSet.ι₁
      (CategoryTheory.CategoryStruct.comp
        (CategoryTheory.SemiCartesianMonoidalCategory.fst X (SSet.stdSimplex.obj (SimplexCategory.mk 1))) f.map) =
    f.map