In Google Colaboratory, I like to create markdown section headers with a prepended number, like so:
# 1. My Notebook
-----
## 1. My section
However, when I look at the Table of Contents pane, the number does not show up.
When I instead use a letter, such as "A", the letter does show up.
How do I fix it so that the prepended numerals (e.g. 1.
) show up in the Table of Contents?