Fix intransitive subtyping issue with SupportsGetItem (#8785)

See python/mypy#13713 for details

Author: hauntsaninja

stdlib/_typeshed/__init__.pyi

@@ -7,7 +7,7 @@ import ctypes
 import mmap
 import pickle
 import sys
-from collections.abc import Awaitable, Callable, Container, Iterable, Set as AbstractSet
+from collections.abc import Awaitable, Callable, Iterable, Set as AbstractSet
 from os import PathLike
 from types import FrameType, TracebackType
 from typing import Any, AnyStr, Generic, Protocol, TypeVar, Union
@@ -118,7 +118,8 @@ class SupportsKeysAndGetItem(Protocol[_KT, _VT_co]):
     def __getitem__(self, __key: _KT) -> _VT_co: ...
 
 # stable
-class SupportsGetItem(Container[_KT_contra], Protocol[_KT_contra, _VT_co]):
+class SupportsGetItem(Protocol[_KT_contra, _VT_co]):
+    def __contains__(self, __x: object) -> bool: ...
     def __getitem__(self, __key: _KT_contra) -> _VT_co: ...
 
 # stable

stdlib/typing.pyi

@@ -447,6 +447,7 @@ class AsyncGenerator(AsyncIterator[_T_co], Generic[_T_co, _T_contra]):
 
 @runtime_checkable
 class Container(Protocol[_T_co]):
+    # This is generic more on vibes than anything else
     @abstractmethod
     def __contains__(self, __x: object) -> bool: ...