add some missing EXAMPLES

<div id="comment:0"></div>

that apparently do not provoke any rst error

Component: **documentation**

Author: **Frédéric Chapoton**

Branch/Commit: **[`a052558`](https://github.com/sagemath/sagetrac-mirror/commit/a052558ad0ccd5afe3293c7457edaa1f0cb8b414)**

Reviewer: **Marc Mezzarobba**

_Issue created by migration from https://trac.sagemath.org/ticket/34602_

