CLN: remove unreachable code in pandas/core/groupby/generic.py::DataFrameGroupBy::_transform_general
Is this part of the code
```
        else:
            # Handle cases like BinGrouper
            return self._concat_objects(keys, values, not_indexed_same=not_indexed_same)
```
necessary? The condition before it is
```
elif self.grouper.groupings is not None
```
. However, even in the case of `BinGrouper`, I don't believe `BinGrouper.groupings` can be `None`:
```
>>> from pandas.core.groupby.ops import BinGrouper
>>> BinGrouper([], []).groupings                                                                                                                                                                   
[Grouping(None)]
```

 and so this code is unreachable. It's not covered by the tests, at least - https://codecov.io/gh/pandas-dev/pandas/src/master/pandas/core/groupby/generic.py#L1354

If it can be removed, I've taken it out and then shifted the code above it back by one tab (because we no longer need the guard)
IIRC the coverage results dont include the slow tests.  did you run those? > IIRC the coverage results dont include the slow tests. did you run those?

Thanks, wasn't aware of that.

Don't they run as part of CI? If so, looks like they still pass @MarcoGorelli still active? Can you address latest comments? Sorry for the delay - yes, I'll get to this during the weekend

EDIT
----
am pretty time constrained right now, will get to this next weekend Closing for now, as I'm busy with other things and have other PRs to respond to: I've opened this up as a good first issue: #33478 .

If nobody takes the issue, I'll come back to it