fact: Definition inverse : Functor ((C1 -> D) * (C2 -> D)) (C1 + C2 -> D).
imports: Functor.Core FunctorCategory.Core Functor.Identity NaturalTransformation.Core Category.Sum Category.Prod Functor.Sum Functor.Prod.Core NaturalTransformation.Sum Functor.Pointwise.Core NaturalTransformation.Paths