old_contents: class Score(object):
      """Represents total user score
      """
      def __init__(self, points=0):
          self.points = points
  
      def __repr__(self):
          return "<Score '{0}' points at {1}>".format(self.points, hex(id(self)))
  
      def add(self, points):
          """Add points to the score
  
          :param points: int number of points to add
          :return: int number of total points
          """
          if int(points) < 0:
              raise ValueError("The number of point must a positive integer, "
                               "got <{0}>".format(points))
          self.points += int(points)
          return self.points
  
      def update(self, n):
          """Update the score according to the length of the chain
  
          :param n: int chain length
          :return: total number of points
          """
          if n < 2:
              raise ValueError("Minimum chain number must be 2, got <{0}>".format(n))
          self.points += (n-1)*5
          return self.points
  
new_contents: class Score(object):
      """Represents total user score
      """
      def __init__(self, points=0):
          self.points = points
  
      def __repr__(self):
          return "<Score '{0}' points at {1}>".format(self.points, hex(id(self)))
  
      def add(self, points):
          """Add points to the score
  
          :param points: int number of points to add
          :return: int number of total points
          """
          if int(points) < 0:
              raise ValueError("The number of point must a positive integer, "
                               "got <{0}>".format(points))
          self.points += int(points)
          return self.points
  
      def update(self, n):
          """Update the score according to the length of the chain
  
          :param n: int chain length
          :return: total number of points
          """
          if n >= 2:
              self.points += (n-1)*5
          return self.points
  
subject: update Score - on empty chain, don't add any points