code: def sort_index(self, **kwargs):
          axis = kwargs.pop("axis", 0)
          index = self.columns if axis else self.index
          ascending = kwargs.pop("ascending", True)
          if ascending is None:
              ascending = False
          kwargs["ascending"] = ascending
          def sort_index_builder(df, **kwargs):
              if axis:
                  df.columns = index
              else:
                  df.index = index
              return df.sort_index(axis=axis, **kwargs)
          func = self._prepare_method(sort_index_builder, **kwargs)
          new_data = self._map_across_full_axis(axis, func)
          if axis:
              new_columns = pandas.Series(self.columns).sort_values(**kwargs)
              new_index = self.index
          else:
              new_index = pandas.Series(self.index).sort_values(**kwargs)
              new_columns = self.columns
          return self.__constructor__(
              new_data, new_index, new_columns, self.dtypes.copy()
          )