@@ -0,0 +1,644 @@
+import sys%0A%0Asys.path.insert(0, %22../linked_list%22)%0Afrom linked_list import Node, IterNode, LinkedList%0A%0A%0Aclass DNode(Node):%0A    def __init__(self, val, link=None, link2=None):%0A        Node.__init__(self, val, link)%0A        self.link2 = link2%0A%0A%0Aclass IterDNode(IterNode):%0A    pass%0A%0A%0Aclass IterDNodeReverse(IterNode):%0A    pass%0A%0A%0Aclass DoublyLinkedList(LinkedList):%0A    def __init__(self):%0A        LinkedList.__init__(self)%0A        self.tail = None%0A%0A    def insert(self, val):%0A        pass%0A%0A    def append(self, val):%0A        pass%0A%0A    def pop(self, val):%0A        pass%0A%0A    def shift(self, val):%0A        pass%0A%0A    def remove(self, val):%0A        pass%0A

add skeleton for Doubly Linked List