old_contents: import cpu
  import memory
  import video
  
  
  class System():
  
      def __init__(self):
          self._cpu = cpu.Cpu()
          self._memory_controller = memory.MemoryController()
          self._video_controller = video.VideoController()
  
      def power_on(self):
          print("System.power_on()")
          self._cpu.power_on()
          self._memory_controller.power_on()
          self._video_controller.power_on()
  
new_contents: import cpu
  import memory
  import video
  
  
  class System():
      """Represents a computer system."""
  
      def __init__(self):
          """Creates and initializes the system components."""
          self._cpu = cpu.Cpu()
          self._memory_controller = memory.MemoryController()
          self._video_controller = video.VideoController()
  
      def power_on(self):
          """Powers on the system components."""
          print("System.power_on()")
          self._cpu.power_on()
          self._memory_controller.power_on()
          self._video_controller.power_on()
  
subject: Add docstrings to system module