code: def reverse_func(apps, schema_editor):
      
      print("\n")
      remove_count = 0
      BackupRun = apps.get_model("backup_app", "BackupRun")
      backup_runs = BackupRun.objects.all()
      for backup_run in backup_runs:
          # Use the origin BackupRun model to get access to get_config_path()
          temp = OriginBackupRun(name=backup_run.name, backup_datetime=backup_run.backup_datetime)
          config_path = temp.get_config_path()
          try:
              config_path.unlink()
          except OSError as err:
              print("ERROR removing config file: %s" % err)
          else:
              remove_count += 1
              # print("%r removed." % config_path.path)
  
      print("%i config files removed.\n" % remove_count)
docs: manage migrate backup_app 0003_auto_20160127_2002