code: def parallel_scan(self, scan_id, target):
          
          try:
              ret = self.exec_scan(scan_id, target)
              if ret == 0:
                  self.add_scan_host_detail(scan_id, name='host_status',
                                            host=target, value='0')
              elif ret == 1:
                  self.add_scan_host_detail(scan_id, name='host_status',
                                            host=target, value='1')
              elif ret == 2:
                  self.add_scan_host_detail(scan_id, name='host_status',
                                            host=target, value='2')
              else:
                  logger.debug('%s: No host status returned', target)
          except Exception as e:
              self.add_scan_error(scan_id, name='', host=target,
                                  value='Host process failure (%s).' % e)
              logger.exception('While scanning %s:', target)
          else:
              logger.info("%s: Host scan finished.", target)
docs: Starts the scan with scan_id.