code: def _add_new_items(self, config, seen):
          '''Add new (unseen) items to the config.'''
          for (key, value) in self.items():
              if key not in seen:
                  self._set_value(config, key, valuef _add_new_items(self, config, seen):
          '''Add new (unseen) items to the config.'''
          for (key, value) in self.items():
              if key not in seen:
                  self._set_value(config, key, value)
docs: Add new (unseen) items to the config.