code: function log_level_plus(logLevel) {
    let index = log_levels.indexOf(logLevel)
    if (index < 0) {
      return []
    } else {
      return log_levels.slice(index, log_levels.length)
    }
  }
docs: It returns the levels above the argument
  @param  {String} logLevel the log level to calculate
  @return {Array}           the list of logs above the argument