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 $\mathsf{C}$.