public Collection<String> getRosterGroupsAllowed() {
        return Collections.unmodifiableCollection(rosterGroupsAllowed);
    }
Returns the roster group(s) allowed to subscribe and retrieve items. This information
is going to be used only when using the
{@link org.jivesoftware.openfire.pubsub.models.RosterAccess} access model.

@return the roster group(s) allowed to subscribe and retrieve items.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/Node.java