done(...args) {
    if (typeof args[args.length - 1] === 'function') {
      // eslint-disable-next-line no-console
      console.warn('Callback function no longer supported as of winston@3.0.0');
      args.pop();
    }

    const info = typeof args[args.length - 1] === 'object' ? args.pop() : {};
    info.level = info.level || 'info';
    info.durationMs = (Date.now()) - this.start;

    return this.logger.write(info);
  }
Ends the current timer (i.e. Profiler) instance and logs the `msg` along
with the duration since creation.
@returns {mixed} - TODO: add return description.
@private