No type hint for Series containing lists of strings in Series.str.split method with expand=False

[pan-vlados]

Describe the bug

The stubs for pandas_stubs.core.strings.StringMethods.split do not return pandas.Series[list[str]] type with expand=False parameter for Series/Index containing lists of strings as described in docs.

To Reproduce

Use VS Code with Pylance extension:

1. The following:

   from pandas import Series
   s = Series(["one", "two"])
   def split(s: "Series[str]") -> "Series[list[str]]":  # error
       return s.str.split(expand=False)
   split(s)

   cause Pylance error below:

   Type "list[str]" cannot be assigned to type variable "S1@Series"
   Type "list[str]" is not assignable to upper bound "Dtype | bytes | date | time | bool | int | float | complex | datetime | timedelta | Period | Interval[Unknown] | CategoricalDtype | BaseOffset" for type variable "S1@Series"
       Type "list[str]" is not assignable to type "Dtype | bytes | date | time | bool | int | float | complex | datetime | timedelta | Period | Interval[Unknown] | CategoricalDtype | BaseOffset"
       "list[str]" is not assignable to "str"
       "list[str]" is not assignable to "bytes"
       "list[str]" is not assignable to "date"
       "list[str]" is not assignable to "time"
       "list[str]" is not assignable to "bool"
       "list[str]" is not assignable to "int"
   ...PylancereportInvalidTypeArguments
   

2. The following is type of "Series[Unknown]":

   from pandas import Series
   s = Series(["one", "two"])
   s = s.str.split(expand=False)
   reveal_type(s)  # Type of "s" is "Series[Unknown]"

Please complete the following information:

• OS : MacOS
• OS Version : Sonoma 14.7.1
• python : 3.10.14
• processor : arm64
• VS Code : 1.96.0 (Universal)
• pandas : 2.2.3
• pandas-stubs : 2.2.3.241126
• Pylance : 2024.12.1