old_contents: """
  Specify the kinds of objects to create using a prototypical instance,
  and create new objects by copying this prototype.
  """
  
  import copy
  
  
  class Prototype:
      """
      Example class to be copied.
      """
  
      pass
  
  
  def main():
      prototype = Prototype()
      prototype_copy = copy.deepcopy(prototype)
  
  
  if __name__ == "__main__":
      main()
  
new_contents: """
  Specify the kinds of objects to create using a prototypical instance,
  and create new objects by copying this prototype.
  """
  
  import copy
  
  
  class Prototype:
      """
      Example class to be copied.
      """
  
      pass
  
  
  def main():
      prototype = Prototype()
      prototype_copy = copy.deepcopy(prototype)
      assert prototype is not prototype_copy
  
  
  if __name__ == "__main__":
      main()
  
subject: Add assert check