code: def sort_index(self, axis=0, level=None, ascending=True, inplace=False,
                     kind='quicksort', na_position='last', sort_remaining=True):
          
          inplace = validate_bool_kwarg(inplace, 'inplace')
          axis = self._get_axis_number(axis)
          axis_name = self._get_axis_name(axis)
          labels = self._get_axis(axis)
  
          if level is not None:
              raise NotImplementedError("level is not implemented")
          if inplace:
              raise NotImplementedError("inplace is not implemented")
  
          sort_index = labels.argsort()
          if not ascending:
              sort_index = sort_index[::-1]
  
          new_axis = labels.take(sort_index)
          return self.reindex(**{axis_name: new_axis})
docs: Sort object by labels (along an axis).
  
          Parameters
          ----------
          axis : {0 or 'index', 1 or 'columns'}, default 0
              The axis along which to sort.  The value 0 identifies the rows,
              and 1 identifies the columns.
          level : int or level name or list of ints or list of level names
              If not None, sort on values in specified index level(s).
          ascending : bool, default True
              Sort ascending vs. descending.
          inplace : bool, default False
              If True, perform operation in-place.
          kind : {'quicksort', 'mergesort', 'heapsort'}, default 'quicksort'
              Choice of sorting algorithm. See also ndarray.np.sort for more
              information.  `mergesort` is the only stable algorithm. For
              DataFrames, this option is only applied when sorting on a single
              column or label.
          na_position : {'first', 'last'}, default 'last'
              Puts NaNs at the beginning if `first`; `last` puts NaNs at the end.
              Not implemented for MultiIndex.
          sort_remaining : bool, default True
              If True and sorting by level and index is multilevel, sort by other
              levels too (in order) after sorting by specified level.
  
          Returns
          -------
          sorted_obj : DataFrame or None
              DataFrame with sorted index if inplace=False, None otherwise.