docs: private static Map<Integer, AdvancedExternalizer<?>> getExternalizersFromProps(StoreProperties props) {
        Map<Integer, AdvancedExternalizer<?>> map = new HashMap<>();
        String externalizers = props.get(MARSHALLER, EXTERNALIZERS);
        if (externalizers != null) {
           for (String ext : externalizers.split(",")) {
              String[] extArray = ext.split(":");
              String className = extArray.length > 1 ? extArray[1] : extArray[0];
              AdvancedExternalizer<?> instance = Util.getInstance(className, SerializationConfigUtil.class.getClassLoader());
              int id = extArray.length > 1 ? new Integer(extArray[0]) : instance.getId();
              map.put(id, instance);
           }
        }
        return map;
     }