code: def _default_poll_callback(self, poll_resp):
          
          if poll_resp.parsed is None:
              return False
          success_list = ['UpdatesComplete', True, 'COMPLETE']
          status = None
          if self.response_format == 'xml':
              status = poll_resp.parsed.find('./Status').text
          elif self.response_format == 'json':
              status = poll_resp.parsed.get(
                  'Status', poll_resp.parsed.get('status'))
          if status is None:
              raise RuntimeError('Unable to get poll response status.')
          return status in success_list
docs: Checks the condition in poll response to determine if it is complete
          and no subsequent poll requests should be done.