class LinkedList:
    def __init__(self):
        self.head = None
        self.tail = None

    def append_left(self, value):
        pass

    def append_right(self, value):
        pass

    def pop_left(self):
        pass

    def pop_right(self):
        pass

    def get_node_iterator(self):
        pass

    def __iter__(self):

    def __add__(self, other):
        pass

    def __iadd__(self, other):
        pass

    def __getitem__(self, index):
        pass

    def __setitem__(self, index, value):
        pass

    def __contains__(self, value):
        pass

    def __reversed__(self):
        pass

    def insert(self):
        pass

    def index(self):
        pass

    def remove(self, value):
        pass

    def sort(self):
        pass