private StringBuilder mergeMarkers(List<Marker> markerList, StringBuilder sb) {
        if(markerList == null || markerList.isEmpty())
            return sb;

        if(sb == null)
            sb = new StringBuilder();

        for(Marker marker : markerList) {
            sb.append(marker);
            sb.append(' ');
        }
        return sb;
    }
Prepend markers and key-value pairs to the message.

@param aLoggingEvent

@return
slf4j-api/src/main/java/org/slf4j/spi/DefaultLoggingEventBuilder.java