# Exercise 2.2. ii of Riehl's book “category theory in context”

Exercise 2.2.ii. Explain why the Yoneda lemma does not dualize to classify natural transformations from an arbitrary set-valued functor to a represented functor.

I don't understand the meaning that "Yoneda lemma does not dualize to classify natural transformations"; Could you explain what it means?

She's asking you to say why the Yoneda lemma does not imply that there is a natural bijection $$\mathrm{Hom}(F,\mathsf{C}(c,-)) \cong Fc$$ for a functor $$F : \mathsf{C} \to \mathbf{Set}$$ and an object $$c$$ of $$\mathsf{C}$$.