How to use the zict.LRU function in zict

def __init__(self, upstream, history=None, key=identity, **kwargs):
        self.seen = dict()
        self.key = key
        if history:
            from zict import LRU
            self.seen = LRU(history, self.seen)

        Stream.__init__(self, upstream, **kwargs)

def setup(self, worker):
        self.cache = Buffer(
            fast={},
            slow=Func(
                dump=blosc.pack_array,
                load=blosc.unpack_array,
                d=Buffer(
                    fast={},
                    slow=LRU(
                        n=self._maxdisk,
                        d=File(os.path.join(worker.local_directory, 'cache')),
                        weight=lambda k, v: len(v),
                    ),
                    n=self._maxcompressed,
                    weight=lambda k, v: len(v),
                ),
            ),
            n=self._maxmem,
            weight=lambda k, v: v.nbytes,
        )
        self.lock = Lock()
        self.hits = 0
        self.misses = 0

def __init__(self, child, history=None, key=identity):
        self.seen = dict()
        self.key = key
        if history:
            from zict import LRU
            self.seen = LRU(history, self.seen)

        Stream.__init__(self, child)