@Override
        public Object add(final Object key, final GeoPrimitive value) {
            Log.d(this.logPraefix + "ADD '" + key + "'");
            addProcessed++;
            addProcessedInBatch++;

            //don't add invalid values
            if (!GeoItem.isValid(value)) {
                return null;
            }
            return providerLayer.add(value);
        }
Key class to be used for entries in MapWriter from a GeoGroup
main/src/main/java/cgeo/geocaching/unifiedmap/geoitemlayer/GeoItemLayer.java