code: def _values_for_argsort(self) -> np.ndarray:
          
          data = self._data.copy()
          data[self._mask] = data.min() - 1
          return data
docs: Return values for sorting.
  
          Returns
          -------
          ndarray
              The transformed values should maintain the ordering between values
              within the array.
  
          See Also
          --------
          ExtensionArray.argsort