docs: public Subscription subscribe(String jid) throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
          PubSub pubSub = createPubsubPacket(Type.set, new SubscribeExtension(jid, getId()));
          PubSub reply = sendPubsubPacket(pubSub);
          return reply.getExtension(PubSubElementType.SUBSCRIPTION);
      }