docs: def _store_unsorted_results(self, smooth, residual):
          """Convert sorted smooth/residual back to as-input order."""
          if self._original_index_of_xvalue:
              # data was sorted. Unsort it here.
              self.smooth_result = numpy.zeros(len(self.y))
              self.cross_validated_residual = numpy.zeros(len(residual))
              original_x = numpy.zeros(len(self.y))
              for i, (xval, smooth_val, residual_val) in enumerate(zip(self.x, smooth, residual)):
                  original_index = self._original_index_of_xvalue[i]
                  original_x[original_index] = xval
                  self.smooth_result[original_index] = smooth_val
                  self.cross_validated_residual[original_index] = residual_val
                  self.x = original_x
          else:
              # no sorting was done. just apply results
              self.smooth_result = smooth
              self.cross_validated_residual = residual