fact: Definition yon {A : Type} `{IsGraph A} (a : A) : A^op -> Type := opyon (A:=A^op) a.
imports: Basics.Overture Basics.Tactics WildCat.Core WildCat.Equiv WildCat.Universe WildCat.Opposite WildCat.FunctorCat WildCat.NatTrans WildCat.Prod WildCat.ZeroGroupoid