code: def update_defaults(self, new_defaults, respect_none=False):
          
          for key, value in six.iteritems(new_defaults):
              item = self.get_item(key)
              if item is None:
                  raise YapconfItemNotFound("Cannot update default for {0}, "
                                            "there is no config item by the "
                                            "name of {1}".format(key, key), None)
  
              item.update_default(value, respect_none)
docs: Update items defaults to the values in the new_defaults dict.
  
          Args:
              new_defaults (dict): A key-value pair of new defaults to be
                  applied.
              respect_none (bool): Flag to indicate if ``None`` values should
                  constitute an update to the default.