new_contents: #!/usr/bin/env python
  # -*- coding:utf-8 -*-
  from __future__ import division
  from __future__ import unicode_literals
  from __future__ import print_function
  
  
  class Node(object):
      def __init__(self, data, next):
          self.data = data
          self.next = next
  
  
  class LinkedList(object):
      def __init__(self):
          self.head = None
  
subject: add sequence datastrucre