old_contents: class StateFader(object):
      """Fades a State Surface in and out from black.
  
      When fading out, the next Game State will automatically take over game
      processing once the fade finishes.
  
      Class Constants:
          FADE_RATE: An integer for the amount of alpha transparency gained or
              lost by the State Surface during each update cycle.
  
      Attributes:
          next_state: An integer for the ID of the next Game State to go to after
              a fade-out. See the StateIDs enum for possible values.
              If this attribute is set to None, it will be assumed that a fade-in
              is meant to play, rather than a fade-out.
          change_state: A method that will remove the current Game State from the
              State stack and switch game processing over to a new State.
          is_running: A Boolean indicating whether the fade is still running.
      """
      FADE_RATE = 7
  
      def __init__(self, change_state):
          """Declare and initialize instance variables.
  
          Args:
              change_state: A method that changes game processing to a new
                  Game States, specified by the ID passed to the method's
                  args.
          """
          self.next_state = None
          self.change_state = change_state
          self.is_running = False
  
      def start_fade_in(self):
          """"""
          self.is_running = True
  
new_contents: class StateFader(object):
      """Fades a State Surface in and out from black.
  
      When fading out, the next Game State will automatically take over game
      processing once the fade finishes.
  
      Class Constants:
          FADE_RATE: An integer for the amount of alpha transparency gained or
              lost by the State Surface during each update cycle.
  
      Attributes:
          next_state: An integer for the ID of the next Game State to go to after
              a fade-out. See the StateIDs enum for possible values.
              If this attribute is set to None, it will be assumed that a fade-in
              is meant to play, rather than a fade-out.
          change_state: A method that will remove the current Game State from the
              State stack and switch game processing over to a new State.
          is_running: A Boolean indicating whether the fade is still running.
      """
      FADE_RATE = 7
  
      def __init__(self, change_state):
          """Declare and initialize instance variables.
  
          Args:
              change_state: A method that changes game processing to a new
                  Game States, specified by the ID passed to the method's
                  args.
          """
          self.next_state = None
          self.change_state = change_state
          self.is_running = False
  
      def start_fade_in(self, state_surf):
          """Begin fading in the State Surface from black.
  
          This will set the State's Surface transparency to 0, in order
          to start the fade-in with a black screen.
  
          Args:
              state_surf: A Surface containing all of a Game State's
                  graphical components.
          """
          state_surf.set_alpha(0)
          self.is_running = True
  
subject: Write start_fade_in()