BUG: df.groupby(col, as_index=False).value_counts() returns a DataFrame but is annotated as Series

Describe the bug

Using

df = pd.DataFrame({"a": [1, 2, 3], "b": 1})

x: pd.DataFrame = df.groupby("a", as_index=False).value_counts()

raises an error, because mypy thinks the return is a Series

 Incompatible types in assignment (expression has type "Series[int]", variable has type "DataFrame")  [assignment]

To Reproduce

1. Provide a minimal runnable pandas example that is not properly checked by the stubs.
2. Indicate which type checker you are using (mypy or pyright).
3. Show the error message received from that type checker while checking your example.

df = pd.DataFrame({"a": [1, 2, 3], "b": 1})

x: pd.DataFrame = df.groupby("a", as_index=False).value_counts()

In theory this should be ok, but not sure if this as_index=False can be typed?

Please complete the following information:

• OS: ubuntu
• OS Version 22.04
• python version 3.10
• version of type checker mypy 0.971
• version of installed pandas-stubs newest 20220815

Additional context Add any other context about the problem here.

[amotzop]

I think as_index is kind of special and changes the return type of many functions, so there is also a third option of breaking SeriesGroupBy and DataFrameGroupBy into 2 different classes depending on as_index and overloading the various functions which return them.

[leesei]

Thanks, this issues was the cloest I got from Googling so I chime in here. 😝