use type annotations in timezones.pyi (pandas-dev#41769)

Author: fangchenli

pandas/_libs/tslibs/timezones.pyi

@@ -1,32 +1,25 @@
+from __future__ import annotations
+
 from datetime import (
     datetime,
     tzinfo,
 )
-from typing import (
-    Callable,
-    Optional,
-    Union,
-)
+from typing import Callable
 
 import numpy as np
 
 # imported from dateutil.tz
 dateutil_gettz: Callable[[str], tzinfo]
 
-
 def tz_standardize(tz: tzinfo) -> tzinfo: ...
-
-def tz_compare(start: Optional[tzinfo], end: Optional[tzinfo]) -> bool: ...
-
+def tz_compare(start: tzinfo | None, end: tzinfo | None) -> bool: ...
 def infer_tzinfo(
-    start: Optional[datetime], end: Optional[datetime],
-) -> Optional[tzinfo]: ...
+    start: datetime | None,
+    end: datetime | None,
+) -> tzinfo | None: ...
 
 # ndarrays returned are both int64_t
 def get_dst_info(tz: tzinfo) -> tuple[np.ndarray, np.ndarray, str]: ...
-
-def maybe_get_tz(tz: Optional[Union[str, int, np.int64, tzinfo]]) -> Optional[tzinfo]: ...
-
-def get_timezone(tz: tzinfo) -> Union[tzinfo, str]: ...
-
-def is_utc(tz: Optional[tzinfo]) -> bool: ...
+def maybe_get_tz(tz: str | int | np.int64 | tzinfo | None) -> tzinfo | None: ...
+def get_timezone(tz: tzinfo) -> tzinfo | str: ...
+def is_utc(tz: tzinfo | None) -> bool: ...