fact: Definition identity_functor_tensor_unit {C : category} (tu : tensor_unit C) : functor_tensor_unit tu tu (functor_identity C).
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Core.NaturalTransformations UniMath.CategoryTheory.Core.Isos