GH992 Fix pd.DataFrame.pct_change fill_method typing (#993)

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* Update new workflow

* GH992 Fix pd.DataFrame.pct_change fill_method typing

* Update pandas-stubs/core/frame.pyi

Co-authored-by: Irv Lustig <irv@princeton.com>

* PR Feedback

---------

Co-authored-by: Irv Lustig <irv@princeton.com>

Author: loicdiridollou

pandas-stubs/core/frame.pyi

@@ -1874,7 +1874,7 @@ class DataFrame(NDFrame, OpsMixin):
     def pct_change(
         self,
         periods: int = ...,
-        fill_method: _str = ...,
+        fill_method: None = ...,
         limit: int | None = ...,
         freq=...,
         **kwargs,

tests/test_frame.py

@@ -2108,6 +2108,11 @@ def test_groupby_series_methods() -> None:
     gb.nth(0).loc[1]
 
 
+def test_dataframe_pct_change() -> None:
+    df = pd.DataFrame({"x": [1, 2, 2, 3, 3], "y": [10, 20, 30, 40, 50]})
+    df.pct_change(fill_method=None)
+
+
 def test_indexslice_setitem():
     df = pd.DataFrame(
         {"x": [1, 2, 2, 3], "y": [1, 2, 3, 4], "z": [10, 20, 30, 40]}