fix @memoize typing annotations and add cache.memoize method

src/yapcache/__init__.py

@@ -1,8 +1,10 @@
 import asyncio
 from functools import wraps
 from typing import (
+    Any,
     Awaitable,
     Callable,
+    Coroutine,
     Optional,
     ParamSpec,
     TypeVar,
@@ -22,7 +24,9 @@ def memoize(
     ttl: float,
     best_before: Callable[[R], Optional[float]] = lambda *a, **kw: None,
     lock: Callable[[str], DistLock] = lambda *a, **kw: NullLock(),
-) -> Callable[[Callable[P, Awaitable[R]]], Callable[P, Awaitable[R]]]:
+) -> Callable[
+    [Callable[P, Coroutine[Any, Any, R]]], Callable[P, Coroutine[Any, Any, R]]
+]:
     update_tasks: dict[str, asyncio.Task] = {}
 
     def decorator(fn: Callable[P, Awaitable[R]]):

src/yapcache/caches/__init__.py

@@ -1,8 +1,12 @@
 import asyncio
-from typing import Any, override
+from typing import Any, Callable, Coroutine, ParamSpec, TypeVar, override
 
+from yapcache import memoize
 from yapcache.cache_item import NOT_FOUND, CacheItem, NotFound
 
+P = ParamSpec("P")
+R = TypeVar("R")
+
 
 class Cache:
     def __init__(self, key_prefix: str = ""):
@@ -25,6 +29,9 @@ async def set(
 
     async def close(self): ...
 
+    def memoize[R](self, fn: Callable[..., Coroutine[Any, Any, R]], *args, **kwargs):
+        return memoize(self, *args, **kwargs)(fn)
+
 
 class MultiLayerCache(Cache):
     def __init__(self, caches: list[Cache] = [], **kwargs):