code: def _add_log_file(filename):
      
      handler = logging.FileHandler(filename)
  
      handler.setLevel(logging.DEBUG)
      formatter = _Formatter(fmt=_logger_fmt,
                             datefmt='%Y-%m-%d %H:%M:%S')
      handler.setFormatter(formatter)
      logging.getLogger().addHandler(handler)
docs: Create a `phy.log` log file with DEBUG level in the
      current directory.