Left derivable stable under pullback

Example 20.1.13. If \(p\colon C \to S\) is left derivable with respect to \(\{W_s\}\), then for any functor \(f\colon T \to S\) the pullback functor \(C \times _S T \to T\) is left derivable with respect to \(\{W_{f(t)}\}_{t \in T}\).