old_contents: """Create a doubly linked list data stucture"""
  
  
  class Node:
      def __init__(self):
          self.prev = None
          self.next = None
          self.data = None
  
  
  class Doubly_LL:
      def __init__(self):
          self.first_n = None
          self.last_n = None
  
      def init_node(self, val):
          new_n = Node()
          new_n.data = val
          return new_n
  
      def first_node(self, new_n):
          self.first_n = new_n
          self.last_n = new_n
  
      def insert(self, val):
          new_n = self.init_node(val)
          if self.first_n is None and self.last_n is None:
              self.first_node(new_n)
          else:
              new_n.next = self.first_n
              self.first_n.prev = new_n
              if self.first_n.next is None:
                  self.last_n = self.first_n
              self.first_n = new_n
  
  
new_contents: """Create a doubly linked list data stucture"""
  
  
  class Node:
      def __init__(self):
          self.prev = None
          self.next = None
          self.data = None
  
  
  class Doubly_LL:
      def __init__(self):
          self.first_n = None
          self.last_n = None
  
      def init_node(self, val):
          new_n = Node()
          new_n.data = val
          return new_n
  
      def first_node(self, new_n):
          self.first_n = new_n
          self.last_n = new_n
  
      def insert(self, val):
          new_n = self.init_node(val)
          if self.first_n is None and self.last_n is None:
              self.first_node(new_n)
          else:
              new_n.next = self.first_n
              self.first_n.prev = new_n
              if self.first_n.next is None:
                  self.last_n = self.first_n
              self.first_n = new_n
  
      def append(self, val):
          new_n = self.init_node(val)
          if self.first_n is None and self.last_n is None:
              self.first_node(new_n)
  
subject: append to empty list passed