> For the complete documentation index, see [llms.txt](https://www.oulan.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.oulan.com/2016/12/18.md).

# 18

![](/files/-MHQ94z_UlApCE1rMUp2)