Update return type of argparse.ArgumentParser._parse_optional (#15124)

Author: yangdanny97

stdlib/argparse.pyi

@@ -249,7 +249,11 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
     def _read_args_from_files(self, arg_strings: list[str]) -> list[str]: ...
     def _match_argument(self, action: Action, arg_strings_pattern: str) -> int: ...
     def _match_arguments_partial(self, actions: Sequence[Action], arg_strings_pattern: str) -> list[int]: ...
-    def _parse_optional(self, arg_string: str) -> tuple[Action | None, str, str | None] | None: ...
+    if sys.version_info >= (3, 12):
+        def _parse_optional(self, arg_string: str) -> list[tuple[Action | None, str, str | None, str | None]] | None: ...
+    else:
+        def _parse_optional(self, arg_string: str) -> tuple[Action | None, str, str | None] | None: ...
+
     def _get_option_tuples(self, option_string: str) -> list[tuple[Action, str, str | None]]: ...
     def _get_nargs_pattern(self, action: Action) -> str: ...
     def _get_values(self, action: Action, arg_strings: list[str]) -> Any: ...