The bug is in the `get_leaves_inside_matching_brackets` on the third line below:
```python
assert xxxxxxxxx.xxxxxxxxx.xxxxxxxxx(
xxxxxxxxx
).xxxxxxxxxxxxxxxxxx(), (
"xxx {xxxxxxxxx} xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
)
```
Including the invisible paren, third line is `).xxxxxxxxxxxxxxxxxx()), (`, that it has a matched pair then an unmatched closing paren afterwards. This PR ensures the returned leaves are actually matched.
Fixes#3414.
