@Override
    public PropertyMap clone() {
        PropertyMap clone = (PropertyMap)super.clone();
        clone.properties = new HashMap<>();
        for (Map.Entry<CompoundName, Object> entry : this.properties.entrySet()) {
            Object cloneValue = cloneHelper.clone(entry.getValue());
            if (cloneValue == null)
                cloneValue = entry.getValue(); // Shallow copy objects which does not support cloning
            clone.properties.put(entry.getKey(), cloneValue);
        }
        return clone;
    }
Returns a direct reference to the map containing the properties set in this instance.
container-search/src/main/java/com/yahoo/search/query/properties/PropertyMap.java