∀ {n m : SimplexCategory} (f : n ⟶ m) (x : ↑(SSet.toTop.obj (SSet.stdSimplex.obj n))),
  m.toTopHomeo ((CategoryTheory.ConcreteCategory.hom (SSet.toTop.map (SSet.stdSimplex.map f))) x) =
    stdSimplex.map (⇑(CategoryTheory.ConcreteCategory.hom f)) (n.toTopHomeo x)