code: def configbase(key):
      
      def decorator(cls):
          parent = cls.getConfigurableParent()
          if parent is None:
              parentbase = None
          else:
              parentbase = getattr(parent, 'configbase', None)
          if parentbase is None:
              base = key
          else:
              base = parentbase + '.' + key
          cls.configbase = base
          cls.configkey = base + '.default'
          return cls
      return decorator
docs: Decorator to set this class to configuration base class. A configuration base class
      uses `<parentbase>.key.` for its configuration base, and uses `<parentbase>.key.default` for configuration mapping.