fact: Definition opposite_functor : Functor cat cat := Build_Functor cat cat (fun C => (C.1^op; has_op _)) (fun _ _ F => F^op)%functor (fun _ _ _ _ _ => idpath) (fun _ => idpath).
imports: Category.Core Functor.Core Category.Dual Functor.Dual Functor.Composition.Core Functor.Identity Cat.Core Functor.Paths Basics.Trunc Types.Sigma HoTT.Tactics Types.Forall