code: def select(self):
          
          err = self._oasis_obj.error
          if np.allclose(err, 0):
              return None
          nsel = self._check_nsel()
          if nsel is None:
              return None
          return self._select(nsel, err)
docs: Selects next column indexes according to defined strategy
  
          Returns
          -------
          cols : ndarray((nsel,), dtype=int)
              selected columns