old_contents: # reverse singly linked list
  
  class Node(object): # define constructor
  	def __init__(self, data):
  		self.data = data
  		self.next = None
  
new_contents: # reverse singly linked list
  
  class Node(object): # define constructor
  	def __init__(self, data):
  		self.data = data
  		self.next = None
  
  class LinkedList(object):
  	def __init__(self, head=None):
  		self.head = head
  
subject: Add linked list class