private String sourceLevel = USER_LEVEL;
        private boolean sourceLevelSet = false;

        public void setSourceLevel(String sourceLevel) {
            if (sourceLevelSet) {
                throw new IllegalStateException("Cannot reset sourceLevel attribute; it is already set to: " + sourceLevel);
            } else if (!(USER_LEVEL.equals(sourceLevel) || GLOBAL_LEVEL.equals(sourceLevel))) {

        if (loggerName == null) {
            return event;
        }
        for (final String name : loggerNames) {
            if (loggerName.startsWith(name)) {
                final Level sourceLevel = event.getLevel();
                if (sourceLevel != Level.ERROR) {
                    return event;
                }
                return new Log4jLogEvent.Builder(event).setLevel(Level.WARN).build();
            }
        }