Level parameter of DataFrame.groupby should allow Sequences

[jens-diewald]

The level parameter of DataFrame.groupby does not except sequences, when it should. (Corresponding Doc)
This is the same as pandas-dev/pandas#47548

To Reproduce
From the linked Issue above

import pandas as pd
df = pd.DataFrame([[1, 2, 3, 4], [5, 6, 7, 8]], columns=['a', 'b', 'c', 'd']).set_index(['a', 'b', 'c'])

print(df.groupby(level=[0, 1]).sum())

My System

• Windows 10
• Python 3.11
• MyPy 1.5.1
• pandas-stubs 2.1.4.231218

Potential Fix
The issue linked above was fixed by changing the type of level from Level | None to IndexLabel | None. (pandas-dev/pandas#47560)
I suppose, the same Fix should be applied to the groupby-Overloads in pandas-stubs/core/frame.pyi.
I am happy to create a pull request, if that helps.
But i would appreciate it, if someone more involved with this library could confirm that the proposed fix makes sense.

[Dr-Irv]

Yes, a PR is welcome, along with tests. Would need to change the type of level in groupby() in frame.pyi and series.pyi for all the overloads.

A test like you have above should suffice, i.e., you don't need to check all the overloads, although it would be good to have a test for both Series and DataFrame.