proposition: Lemma diag_functor_fmonoidal_assoc : preserves_associativity (fmonoidal_preservestensordata diag_functor_fmonoidal_data).
proof: Proof. intros x y z. refine (_ @ inner_swap_hexagon'_3 V x y z @ _). - now rewrite <- (when_bifunctor_becomes_rightwhiskering V). - now rewrite <- (when_bifunctor_becomes_leftwhiskering V). Qed.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Monoidal.WhiskeredBifunctors UniMath.CategoryTheory.Monoidal.Categories UniMath.CategoryTheory.Monoidal.Functors UniMath.CategoryTheory.Monoidal.Structure.Symmetric UniMath.CategoryTheory.Monoidal.Structure.SymmetricDiagonal