human
Solve the following python programming problem given the following code:
def lru_cache(maxsize = 100, typed = False) : 
    'Least-recently-used cache decorator, see:
        http://docs.python.org/3/library/functools.html#functools.lru_cache
        ' 
    def decorating_function(user_function) : 
        cache = dict () 
        stats = [0, 0] 
        (HITS, MISSES) = (0, 1) 
        make_key = _make_key 
        cache_get = cache.get 
        _len = len 
        lock = RLock () 
        root = [] 
        root [:] = [root, root, None, None] 
        nonlocal_root = [root] 
        (PREV, NEXT, KEY, RESULT) = (0, 1, 2, 3) 
        if (maxsize == 0) : 
            def wrapper(* args, **kwds) : 
                result = user_function (* args, ** kwds) 
                stats [MISSES] += 1 
                return result 
else : 
            if (maxsize is None) : 
                def wrapper(* args, **kwds) : 
                    key = make_key (args, kwds, typed) 
                    result = cache_get (key, root) 
                    if (result is not root) : 
                        stats [HITS] += 1 
                        return result 
result = user_function (* args, ** kwds) 
                    cache [key] = result 
                    stats [MISSES] += 1 
                    return result 
else : 
                def wrapper(* args, **kwds) : 
                    if (kwds or typed) : 
                        key = make_key (args, kwds, typed) 
else : 
                        key = args 
lock.acquire () 
                    try : 
                        link = cache_get (key) 
                        if (link is not None) : 
                            (root,) = nonlocal_root 
                            (link_prev, link_next, key, result) = link 
                            link_prev [NEXT] = link_next 
                            link_next [PREV] = link_prev 
                            last = root [PREV] 
                            last [NEXT] = root [PREV] = link 
                            link [PREV] = last 
                            link [NEXT] = root 
       ...
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def decorating_function(