[multiprocessing.queues] Add missing pickle methods (#15424)

Author: emmanuel-ferdman

stdlib/multiprocessing/queues.pyi

@@ -1,15 +1,21 @@
 import sys
 from types import GenericAlias
-from typing import Any, Generic, TypeVar
+from typing import Any, Generic, NewType, TypeVar
 
 __all__ = ["Queue", "SimpleQueue", "JoinableQueue"]
 
 _T = TypeVar("_T")
 
+_QueueState = NewType("_QueueState", object)
+_JoinableQueueState = NewType("_JoinableQueueState", object)
+_SimpleQueueState = NewType("_SimpleQueueState", object)
+
 class Queue(Generic[_T]):
     # FIXME: `ctx` is a circular dependency and it's not actually optional.
     # It's marked as such to be able to use the generic Queue in __init__.pyi.
     def __init__(self, maxsize: int = 0, *, ctx: Any = ...) -> None: ...
+    def __getstate__(self) -> _QueueState: ...
+    def __setstate__(self, state: _QueueState) -> None: ...
     def put(self, obj: _T, block: bool = True, timeout: float | None = None) -> None: ...
     def get(self, block: bool = True, timeout: float | None = None) -> _T: ...
     def qsize(self) -> int: ...
@@ -24,13 +30,17 @@ class Queue(Generic[_T]):
         def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 class JoinableQueue(Queue[_T]):
+    def __getstate__(self) -> _JoinableQueueState: ...  # type: ignore[override]
+    def __setstate__(self, state: _JoinableQueueState) -> None: ...  # type: ignore[override]
     def task_done(self) -> None: ...
     def join(self) -> None: ...
 
 class SimpleQueue(Generic[_T]):
     def __init__(self, *, ctx: Any = ...) -> None: ...
     def close(self) -> None: ...
     def empty(self) -> bool: ...
+    def __getstate__(self) -> _SimpleQueueState: ...
+    def __setstate__(self, state: _SimpleQueueState) -> None: ...
     def get(self) -> _T: ...
     def put(self, obj: _T) -> None: ...
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...