@Override
    public Object get(CompoundName key, Map<String,String> context,
                      com.yahoo.processing.request.Properties substitution) {
        if(key == null) return null;
        Object result = parent.get(getPathPrefix() + "." + key,context,substitution);
        if(result == null) {
            return super.get(key,context,substitution);
        } else {
            return result;
        }
    }
A wrapper around a chain of property objects that prefixes all gets/sets with a given path

@author Arne Bergene Fossaa
@deprecated Unused and will go away on vespa 9
container-search/src/main/java/com/yahoo/search/query/properties/SubProperties.java