old_contents: import memory
  import video
  
  
  class System():
  
      def __init__(self):
          self.__memory_controller = memory.MemoryController()
          self.__video_controller = video.VideoController()
  
      def power_on(self):
          self.__memory_controller.power_on()
          self.__video_controller.power_on()
  
new_contents: import memory
  import video
  
  
  class System():
  
      def __init__(self):
          self.__memory_controller = memory.MemoryController()
          self.__video_controller = video.VideoController()
  
      def power_on(self):
          print("System.power_on()")
          self.__memory_controller.power_on()
          self.__video_controller.power_on()
  
subject: Add power_on debug output to system module