fact: Fixpoint vec_trie `(x : Vector.t a (size s)) : vec (trie x) = x.
imports: Category.Lib Category.Theory.Category Category.Theory.Isomorphism Category.Theory.Functor Category.Theory.Adjunction Category.Structure.Terminal Category.Structure.Cartesian Category.Structure.BiCCC Category.Instance.Fun Category.Instance.Coq Category.Instance.Sets Coq.Vectors.Vector