Big diff: Use new "|" union syntax (#5872)

stdlib/email/policy.pyi

@@ -3,10 +3,10 @@ from email.contentmanager import ContentManager
 from email.errors import MessageDefect
 from email.header import Header
 from email.message import Message
-from typing import Any, Callable, List, Optional, Tuple, Union
+from typing import Any, Callable, List, Tuple
 
 class Policy:
-    max_line_length: Optional[int]
+    max_line_length: int | None
     linesep: str
     cte_type: str
     raise_on_defect: bool
@@ -15,7 +15,7 @@ class Policy:
     def clone(self, **kw: Any) -> Policy: ...
     def handle_defect(self, obj: Message, defect: MessageDefect) -> None: ...
     def register_defect(self, obj: Message, defect: MessageDefect) -> None: ...
-    def header_max_count(self, name: str) -> Optional[int]: ...
+    def header_max_count(self, name: str) -> int | None: ...
     @abstractmethod
     def header_source_parse(self, sourcelines: List[str]) -> Tuple[str, str]: ...
     @abstractmethod
@@ -30,7 +30,7 @@ class Policy:
 class Compat32(Policy):
     def header_source_parse(self, sourcelines: List[str]) -> Tuple[str, str]: ...
     def header_store_parse(self, name: str, value: str) -> Tuple[str, str]: ...
-    def header_fetch_parse(self, name: str, value: str) -> Union[str, Header]: ...  # type: ignore
+    def header_fetch_parse(self, name: str, value: str) -> str | Header: ...  # type: ignore
     def fold(self, name: str, value: str) -> str: ...
     def fold_binary(self, name: str, value: str) -> bytes: ...