cachetools memoizing attributes (cache, key, lock) are not available

import cachetools
import threading

## cached function

@cachetools.cached(cache=cachetools.LRUCache(maxsize=10),
                   key=lambda x, y: y,
                   lock=threading.Lock())
def fun(x: str, y: str) -> str:
    return y

print(fun('ignored', 'hello world'))
with fun.cache_lock:
    print(fun.cache[fun.cache_key('ignored', 'hello world')])
fun.cache_clear()

## cached method

class Class:
    def __init__(self):
        self.cache = cachetools.LRUCache(maxsize=10)
        self.lock = threading.Lock()

    @cachetools.cachedmethod(cache=lambda self: self.cache,
                             key=lambda self, x, y: y,
                             lock=lambda self: self.lock)
    def meth(self, x: str, y: str) -> str:
        return y

c = Class()
print(c.meth('ignored', 'hello world'))
with c.meth.cache_lock(c):
    print(c.meth.cache(c)[c.meth.cache_key(c, 'ignored', 'hello world')])

I’m not sure if this is the “intended” way to use the memoizing attributes of a cached method (passing in c for the self argument explicitly), but it seems to work at runtime, at least. (Personally, I’d be fine with support just for @cached functions, but I figured it makes sense to include @cachedmethod in the example too.)