docs: public List<Subscription> getSubscriptions() throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
          Stanza reply = sendPubsubPacket(Type.get, new NodeExtension(PubSubElementType.SUBSCRIPTIONS), null);
          SubscriptionsExtension subElem = reply.getExtension(PubSubElementType.SUBSCRIPTIONS.getElementName(), PubSubElementType.SUBSCRIPTIONS.getNamespace().getXmlns());
          return subElem.getSubscriptions();
      }