functools: add cache (#4089)

Co-authored-by: hauntsaninja <>

stdlib/3/functools.pyi

@@ -109,3 +109,5 @@ if sys.version_info >= (3, 9):
         def static_order(self) -> Iterable[_T]: ...
 
     class CycleError(ValueError): ...
+
+    def cache(__user_function: Callable[..., _T]) -> _lru_cache_wrapper[_T]: ...