Add functools._make_key (#5370)

* Add functools._make_key

* Added _HashedSeq class

stdlib/functools.pyi

@@ -1,5 +1,5 @@
 import sys
-from _typeshed import SupportsLessThan
+from _typeshed import SupportsItems, SupportsLessThan
 from typing import (
     Any,
     Callable,
@@ -7,10 +7,13 @@ from typing import (
     Generic,
     Hashable,
     Iterable,
+    List,
     Mapping,
     NamedTuple,
     Optional,
     Sequence,
+    Set,
+    Sized,
     Tuple,
     Type,
     TypeVar,
@@ -131,3 +134,20 @@ if sys.version_info >= (3, 8):
 
 if sys.version_info >= (3, 9):
     def cache(__user_function: Callable[..., _T]) -> _lru_cache_wrapper[_T]: ...
+
+class _HashedSeq(Generic[_T], List[_T]):
+    __slots__: str
+    hashvalue: int
+    def __init__(self, tup: Tuple[Any, ...], hash: Callable[[object], int] = ...) -> None: ...
+    def __hash__(self) -> int: ...  # type: ignore
+
+def _make_key(
+    args: Tuple[Hashable, ...],
+    kwds: SupportsItems[Any, Any],
+    typed: bool,
+    kwd_mark: Tuple[object, ...] = ...,
+    fasttypes: Set[type] = ...,
+    tuple: type = ...,
+    type: Any = ...,
+    len: Callable[[Sized], int] = ...,
+) -> Union[Hashable, _HashedSeq[Any]]: ...