fact: Definition group {a : Type} (m n : nat) (xs : t a (m * n)) : t (t a n) m := `1 (group_dep m n xs).
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