old_contents: 
  #--IMPORT_ALL_FROM_FUTURE--#
  
  import sys
  from . import mouse
  from . import keyboard
  from . import window
  from . import screen
new_contents: 
  #--IMPORT_ALL_FROM_FUTURE--#
  
  import sys
  from . import mouse
  from . import keyboard
  from . import screen
subject: Package need not to declared in __init__.py