$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
4.35
\begin{equation} \label{diagram:categorical-pushout-lemma} \begin{gathered} \xymatrix@R =50pt@C=50pt{ \operatorname{Fun}(A,\operatorname{\mathcal{C}})^{\simeq } & \operatorname{Fun}(A_0,\operatorname{\mathcal{C}})^{\simeq } \ar [l]_{u} \\ \operatorname{Fun}(A_1,\operatorname{\mathcal{C}})^{\simeq } \ar [u] & \operatorname{Fun}(A_{01},\operatorname{\mathcal{C}})^{\simeq }, \ar [l]_{u'} \ar [u] } \end{gathered} \end{equation}