code: def argsort(self, *args, **kwargs):
          
          nv.validate_argsort(args, kwargs)
  
          if self._step > 0:
              return np.arange(len(self))
          else:
              return np.arange(len(self) - 1, -1, -1)
docs: Returns the indices that would sort the index and its
          underlying data.
  
          Returns
          -------
          argsorted : numpy array
  
          See Also
          --------
          numpy.ndarray.argsort