def _get_formatter():
    """
    Get the string of log formatter.

    Returns:
        str, the string of log formatter.
    """
    formatter = (
        '[%(levelname)s] %(sub_module)s(%(process)d:%(thread)d,%(processName)s):%(asctime)s [%(filepath)s:%(lineno)d] %(message)s'
        )
    return formatter
