code: def flush(self, exclude=None, include=None, dryrun=False):
          '''Flush :attr:`registered_models`.
  
          :param exclude: optional list of model names to exclude.
          :param include: optional list of model names to include.
          :param dryrun: Doesn't remove anything, simply collect managers
              to flush.
          :return:
          '''
          exclude = exclude or []
          results = []
          for manager in self._registered_models.values():
              m = manager._meta
              if include is not None and not (m.modelkey in include or
                                              m.app_label in include):
                  continue
              if not (m.modelkey in exclude or m.app_label in exclude):
                  if dryrun:
                      results.append(manager)
                  else:
                      results.append(manager.flush())
          return resultf flush(self, exclude=None, include=None, dryrun=False):
          '''Flush :attr:`registered_models`.
  
          :param exclude: optional list of model names to exclude.
          :param include: optional list of model names to include.
          :param dryrun: Doesn't remove anything, simply collect managers
              to flush.
          :return:
          '''
          exclude = exclude or []
          results = []
          for manager in self._registered_models.values():
              m = manager._meta
              if include is not None and not (m.modelkey in include or
                                              m.app_label in include):
                  continue
              if not (m.modelkey in exclude or m.app_label in exclude):
                  if dryrun:
                      results.append(manager)
                  else:
                      results.append(manager.flush())
          return results
docs: Flush :attr:`registered_models`.
  
          :param exclude: optional list of model names to exclude.
          :param include: optional list of model names to include.
          :param dryrun: Doesn't remove anything, simply collect managers
              to flush.
          :return: