fact: Definition tensor_unit_to_tensor {C : category} (tu : tensor_unit C) : tensor C := pr1 tu.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Core.NaturalTransformations UniMath.CategoryTheory.Core.Isos