new_contents: class Node(object):
      def __init__(self, val, prev=None, next_=None):
          self.val = val
          self.prev = prev
          self.next = next_
  
      def __repr__(self):
          return '{val}'.format(val=self.val)
  
  
  class DoublLinkedList(object):
      def __init__(self, iterable=()):
          self._current = None
          self.head = None
          self.tail = None
          self.length = 0
          for val in reversed(iterable):
              self.insert(val)
  
      def __repr__(self):
          node = self.head
          output = ''
          for node in self:
              output += '{!r}, '.format(node.val)
          return '({})'.format(output.rstrip(' ,'))
  
      def __len__(self):
          return self.length
  
      def __iter__(self):
          if self.head is not None:
              self._current = self.head
          return self
  
      def next(self):
          pass
  
      def size(self):
          pass
  
      def search(self, search):
          pass
  
      def remove(self, search):
          pass
  
      def insert(self, val):
          pass
  
      def append(self, val):
          pass
  
      def pop(self):
          pass
  
      def shift(self):
          pass
  
      def display(self):
          ''''''
          return repr(self)
  
subject: Add structure and methods to double linked list.