On traces of #33982
To pay attention on https://github.com/pandas-dev/pandas/pull/33982#issuecomment-643246205. Sorry, I don't know another way now.

/cc @mproszewska , @jreback

Thanks.
Can you clarify what this is for? I didn't understand from the comment linked @WillAyd , #33982 introduces `index_col` argument in `_is_potential_multi_index`:
```diff
- def _is_potential_multi_index(columns):
+ def _is_potential_multi_index(
+     columns, index_col: Optional[Union[bool, Sequence[int]]] = None
+ ):
```

There are two usages of this function in Pandas:
1. https://github.com/pandas-dev/pandas/blob/v1.0.5/pandas/io/parsers.py#L1526
2. https://github.com/pandas-dev/pandas/blob/v1.0.5/pandas/io/parsers.py#L1547

#33982 modifies first call only. In that comment I ask if it is correct. @kuraga - might be worth adding a test to highlight what functionality this changes? Closing as its not clear what this is or solves; if you can clarify further and add a test case can certainly reopen @WillAyd , it solves nothing. It demonstrates https://github.com/pandas-dev/pandas/pull/33982#issuecomment-643246205 @kuraga ia this actually a bug?

iow can u hit the line of code u added?