pandas droplevel missing some argument types

[Dr-Irv]

Environment data

• Language Server version: 2020.9.5
• OS and version: Windows 10
• Python version (& distribution if applicable, e.g. Anaconda): Anaconda Python 3.7.5

Expected behaviour

No error

Actual behaviour

mi3 : pd.Index = pd.MultiIndex.from_product([[1, 2], [3, 4], [5, 6]], names=["a", "b", "c"])
mi4 = mi3.droplevel("a")
mi4 = mi3.droplevel(["a", "b"])
s = pd.Series([i for i in range(len(mi3))], index=mi3)
s2 = s.droplevel(["a", "b"])
df = s.to_frame("s")
df3 = df.droplevel(["a", "b"])

Get errors as follows on lines 2, 3, 5 and 7 respectively. droplevel() allows string and list of string arguments

Argument of type "Literal['a']" cannot be assigned to parameter "level" of type "int" in function "droplevel"
  "Literal['a']" is incompatible with "int"

Argument of type "List[str]" cannot be assigned to parameter "level" of type "int" in function "droplevel"
  "List[str]" is incompatible with "int"

Argument of type "List[str]" cannot be assigned to parameter "level" of type "Level" in function "droplevel"
  Type "List[str]" cannot be assigned to type "Level"
    "__hash__" is an incompatible type
    Cannot assign to "None"
    "List[str]" is incompatible with "int"
      Type "None" cannot be assigned to type "(self: Unknown) -> int"

Argument of type "List[str]" cannot be assigned to parameter "level" of type "Level" in function "droplevel"
  Type "List[str]" cannot be assigned to type "Level"
    "__hash__" is an incompatible type
    Cannot assign to "None"
    "List[str]" is incompatible with "int"
      Type "None" cannot be assigned to type "(self: Unknown) -> int"

Fixes are as follows:

diff core/frame.pyi.ORIG core/frame.pyi
2924c2925
<     def droplevel(self, level: Level = ..., axis: AxisType = ...) -> DataFrame: ...
---
>     def droplevel(self, level: Union[Level, List[Level]] = ..., axis: AxisType = ...) -> DataFrame: ...

diff core/series.pyi.ORIG core/series.pyi
1598c1599
<     def droplevel(self, level: Level, axis: SeriesAxisType = ...) -> DataFrame: ...
---
>     def droplevel(self, level: Union[Level, List[Level]], axis: SeriesAxisType = ...) -> DataFrame: ...

diff core/indexes/base.pyi.ORIG core/indexes/base.pyi
2c2
< from pandas._typing import Dtype, Label, T1, T2, np_ndarray_str, np_ndarray_int64
---
> from pandas._typing import Dtype, Label, Level, T1, T2, np_ndarray_str, np_ndarray_int64
76c76
<     def droplevel(self, level: int = ...): ...
---
>     def droplevel(self, level: Union[Label, List[Label]] = ...): ...

[jakebailey]

This issue has been fixed in version 2020.9.6, which we've just released. You can find the changelog here: https://github.com/microsoft/pylance-release/blob/master/CHANGELOG.md#202096-23-september-2020