fact: Definition monoidal_to_tensor_unit {C : category} (M : monoidal C) : tensor_unit C := monoidal_tensor M ,, monoidal_unit M.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Monoidal.WhiskeredBifunctors UniMath.CategoryTheory.Monoidal.Categories