possible error in documentation
The page

https://pandas.pydata.org/pandas-docs/stable/user_guide/missing_data.html#string-regular-expression-replacement

seems to have an example that can be improved. The page lists

```python
df.replace([r'\.', r'(a)'], ['dot', '\1stuff'], regex=True)
```
as an example. However '\1' is ignored because the replacement regex is not a raw string. I think what you mean is likely

```python
df.replace([r'\.', r'(a)'], ['dot', r'\1stuff'], regex=True)
```

if my understanding is correct please consider updating the page.

Regards,

Panos Karamertzanis

