How to sort TOC entries

Hi,

I am struggling to sort the entries of the `.. toctree::` in documentation generated with `autoapi`. I have one `<submodule>.piy` sutbfile for each of my project's submodule and it seems they are shown in the TOC in the order they appear rather than in alphabetical order.

I haven't found a way to sort those entries from the available documentation. Am I missing something?