code: def add_on_results(self):
          
          if self._add_on_results is None:
              self._add_on_results = AddOnResultList(
                  self._version,
                  account_sid=self._solution['account_sid'],
                  reference_sid=self._solution['sid'],
              )
          return self._add_on_results
docs: Access the add_on_results
  
          :returns: twilio.rest.api.v2010.account.recording.add_on_result.AddOnResultList
          :rtype: twilio.rest.api.v2010.account.recording.add_on_result.AddOnResultList