fact: Variable Y : C.
imports: Category.Core Functor.Core NaturalTransformation.Core Functor.Identity Functor.Composition.Core Functor.Dual Category.Dual Adjoint.Core Adjoint.UnitCounit Adjoint.UnitCounitCoercions Adjoint.Dual UniversalProperties Comma.Dual InitialTerminalCategory.Core InitialTerminalCategory.Functors