Example 2.2.8.7. Let $\operatorname{\mathcal{C}}$ be an ordinary category, viewed as a $2$-category having only identity $2$-morphisms (Remark 2.2.1.6). Then $\operatorname{\mathcal{C}}$ is a $(2,1)$-category.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$