Design an LRU cache

%%writefile lru_cache.py
class Node(object):

    def __init__(self, results):        self.results = results        self.prev = None        self.next = Noneclass LinkedList(object):    def __init__(self):        self.head = None        self.tail = None    def move_to_front(self, node):  # ...    def append_to_front(self, node):  # ...    def remove_from_tail(self):  # ...class Cache(object):    def __init__(self, MAX_SIZE):        self.MAX_SIZE = MAX_SIZE        self.size = 0        self.lookup = {}  # key: query, value: node        self.linked_list = LinkedList()    def get(self, query)        """Get the stored query result from the cache.
        
        Accessing a node updates its position to the front of the LRU list.
        """        node = self.lookup.get(query)        if node is None:            return None        self.linked_list.move_to_front(node)        return node.results    def set(self, results, query):        """Set the result for the given query key in the cache.
        
        When updating an entry, updates its position to the front of the LRU list.
        If the entry is new and the cache is at capacity, removes the oldest entry
        before the new entry is added.
        """        node = self.lookup.get(query)        if node is not None:            # Key exists in cache, update the value            node.results = results            self.linked_list.move_to_front(node)        else:            # Key does not exist in cache            if self.size == self.MAX_SIZE:                # Remove the oldest entry from the linked list and lookup                self.lookup.pop(self.linked_list.tail.query, None)                self.linked_list.remove_from_tail()            else:                self.size += 1            # Add the new key and value            new_node = Node(results)            self.linked_list.append_to_front(new_node)            self.lookup[query] = new_node