No need for the `#`. Just the explanation line, optionally ending with a `:`, then a blank line, and then the code example. In that case, the code example will be rendered nicely as code. Like this:
```
A pattern with more than one group will return a DataFrame:

>>> Series(['a1', 'b2', 'c3']).str.extract('([ab])(\d)')

Named groups will become column names in the result:
...
```