$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
4.37
\begin{equation} \label{diagram:categorical-pushout-lemma2} \begin{gathered} \xymatrix@R =50pt@C=50pt{ \operatorname{Fun}(A,\operatorname{\mathcal{C}}) & \operatorname{Fun}(A_0,\operatorname{\mathcal{C}}) \ar [l]_{u} \\ \operatorname{Fun}(A_1,\operatorname{\mathcal{C}}) \ar [u] & \operatorname{Fun}(A_{01},\operatorname{\mathcal{C}}), \ar [l] \ar [u] } \end{gathered} \end{equation}