code: def _qmed_from_amax_records(self):
          
          valid_flows = valid_flows_array(self.catchment)
          n = len(valid_flows)
          if n < 2:
              raise InsufficientDataError("Insufficient annual maximum flow records available for catchment {}."
                                          .format(self.catchment.id))
          return np.median(valid_flows)
docs: Return QMED estimate based on annual maximum flow records.
  
          :return: QMED in m³/s
          :rtype: float