class MessageBrokerClient extends Client {

    public void subscribeToTopic(String topicName) throws EtiqetException {
        getTransport().subscribeToTopic(
            Optional.of(topicName),
            message -> addMessageToGroup(messagesByTopic, topicName, message)
        );
    }

    public  MessageBrokerClient(String clientConfig);
    public  MessageBrokerClient(String primaryClientConfig, String secondaryClientConfig);
    public  MessageBrokerClient(String primaryClientConfig, String secondaryClientConfig, ProtocolConfig protocol);

}