fixLastLevel = data => {
    try {
      const log = JSON.parse(data)
      ms.lastLevel = log.level
    } catch (e) {
      ms.lastLevel = 30 // info level as fallback
    }
  }
Before write() of multistream is called the actual log level
is set in write() in proto.js. We emulate that behavior here
to call write() of multistream directly to inject/forward
the log message to the real loggers.

@param {string} data