code: func (l *FileLog) EmitAuditEvent(event Event, fields EventFields) error {
  	// see if the log needs to be rotated
  	err := l.rotateLog()
  	if err != nil {
  		log.Error(err)
  	}
  	err = UpdateEventFields(event, fields, l.Clock, l.UIDGenerator)
  	if err != nil {
  		log.Error(err)
  	}
  	// line is the text to be logged
  	line, err := json.Marshal(fields)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	// log it to the main log file:
  	if l.file != nil {
  		fmt.Fprintln(l.file, string(line))
  	}
  	return nil
  }
docs: // EmitAuditEvent adds a new event to the log. Part of auth.IFileLog interface.