Update type hints to align util/testing.py and picke.py

Author: TomoyukiSuzuki-Aidea

pandas/io/pickle.py

@@ -1,16 +1,16 @@
 """ pickle compat """
 import pickle
-from typing import Any, Optional
+from typing import Optional
 import warnings
 
-from pandas._typing import FilePathOrBuffer
+from pandas._typing import FilePathOrBuffer, FrameOrSeries
 from pandas.compat import pickle_compat as pc
 
 from pandas.io.common import get_filepath_or_buffer, get_handle
 
 
 def to_pickle(
-    obj: Any,
+    obj: FrameOrSeries,
     filepath_or_buffer: FilePathOrBuffer,
     compression: Optional[str] = "infer",
     protocol: int = pickle.HIGHEST_PROTOCOL,
@@ -20,7 +20,7 @@ def to_pickle(
 
     Parameters
     ----------
-    obj : any object
+    obj : any pandas object
         Any python object.
     filepath_or_buffer : str, path object or file-like object
         File path, URL, or buffer where the pickled object will be stored.

pandas/util/testing.py

@@ -22,7 +22,7 @@
 )
 
 import pandas._libs.testing as _testing
-from pandas._typing import FrameOrSeries
+from pandas._typing import FilePathOrBuffer, FrameOrSeries
 from pandas.compat import _get_lzma_file, _import_lzma
 
 from pandas.core.dtypes.common import (
@@ -101,7 +101,9 @@ def reset_display_options():
     pd.reset_option("^display.", silent=True)
 
 
-def round_trip_pickle(obj: FrameOrSeries, path: Optional[str] = None) -> FrameOrSeries:
+def round_trip_pickle(
+    obj: FrameOrSeries, path: FilePathOrBuffer = None
+) -> FrameOrSeries:
     """
     Pickle an object and then read it again.