def METHOD_NAME(self):
    if self.cache_head is None and self.cache_tail is None:
        return None
    elif self.cache_head == self.cache_tail:
        cache_head = self.cache_head
        self.cache_head = self.cache_tail = None
        return cache_head
    else:
        cache_head = self.cache_head
        self.cache_head.nxt.pre = None
        self.cache_head = self.cache_head.nxt
        return cache_head