def pre_save_handler(sender, instance, **kwargs):
 now = timezone.now()
 if (instance.id is None):
  instance.creation_date = now
 instance.modification_date = now

def pre_save_handler ( sender , instance , ** kwargs ) : now = timezone . now ( ) if ( instance . id is None ) : instance . creation_date = now instance . modification_date = now
intercept attempts to save and sort the tag field alphabetically .