Multiple markers not handled correctly about logback-gelf HOT 4 CLOSED

    /**
     * Adds the given marker as a reference, and returns this marker.
     * <p>
     * This can be used to chain markers together fluently on a log line. For example:
     * 
     * <pre>
     * {@code
     * import static net.logstash.logback.marker.Markers.*
     *     
     * logger.info(append("name1", "value1).and(append("name2", "value2")), "log message");
     * }
     * </pre>
     * 
     * @param <T> subtype of LogstashMarker
     * @param reference The marker to add
     * @return A marker with this marker and the given marker
     */
    @SuppressWarnings("unchecked")
    public <T extends LogstashMarker> T and(Marker reference) {
        add(reference);
        return (T) this;
    }

public String toString() {
     String self = toStringSelf();
     if (!hasReferences()) {
         return self;
     }

     StringBuilder sb = new StringBuilder(self);
     boolean appendSeparator = !self.isEmpty();
     for (Marker marker : this) {
         if (appendSeparator) {
             sb.append(", ");
         }
         String referenceToString = marker.toString();
         sb.append(referenceToString);
         appendSeparator = !referenceToString.isEmpty();
     }

     return sb.toString();
 }

    @Override
    public void writeTo(JsonGenerator generator) throws IOException {
        if (map != null) {
            for (Map.Entry<?, ?> entry : map.entrySet()) {
                generator.writeFieldName(String.valueOf(entry.getKey()));
                generator.writeObject(entry.getValue());
            }
        }
    }