code: public void unsubscribe(String jid, String subscriptionId) throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
          sendPubsubPacket(createPubsubPacket(Type.set, new UnsubscribeExtension(jid, getId(), subscriptionId)));
      }
docs: Remove the specific subscription related to the specified JID.
  
  @param jid The JID used to subscribe to the node
  @param subscriptionId The id of the subscription being removed
  @throws XMPPErrorException
  @throws NoResponseException
  @throws NotConnectedException
  @throws InterruptedException