code: def _default(cls, opts):
          
          level = getattr(logging, opts.log_level, logging.DEBUG)
  
          logger = logging.getLogger('luigi-interface')
          logger.setLevel(level)
  
          stream_handler = logging.StreamHandler()
          stream_handler.setLevel(level)
  
          formatter = logging.Formatter('%(levelname)s: %(message)s')
          stream_handler.setFormatter(formatter)
  
          logger.addHandler(stream_handler)
          return True
docs: Setup default logger