code: public boolean enable(Jid pushJid, String node)
              throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
          return enable(pushJid, node, null);
      }
docs: Enable push notifications.
  
  @param pushJid
  @param node
  @return true if it was successfully enabled, false if not
  @throws NoResponseException
  @throws XMPPErrorException
  @throws NotConnectedException
  @throws InterruptedException