private void expandRelatedModelGroupComponents(XSModelGroup modelGroup, Vector componentList,
            String namespace, Map<String, Vector> dependencies) {
        XSObjectList particles = modelGroup.getParticles();
        final int length = (particles == null) ? 0 : particles.getLength();
        for (int i=0; i<length; i++) {
            expandRelatedParticleComponents((XSParticle)particles.item(i), componentList, namespace, dependencies);
        }
    }