code: public Response unsubscribe(String topic, String callbackUrl, JinxConstants.VerificationMode mode, String verificationToken) throws JinxException {
      JinxUtils.validateParams(topic, callbackUrl, mode);
      Map<String, String> params = new TreeMap<>();
      params.put("method", "flickr.push.unsubscribe");
      params.put("topic", topic);
      params.put("callback", callbackUrl);
      params.put("verify", mode.toString());
      if (!JinxUtils.isNullOrEmpty(verificationToken)) {
        params.put("verify_token", verificationToken);
      }
      return jinx.flickrGet(params, Response.class);
    }
docs: Unsubscribe from a push feed.
  
  (this method is experimental and may change)
  
  This method requires authentication with 'read' permission.
  
  @param topic             the type of subscription. Required.
  @param callbackUrl       url for the subscription endpoint. Must be the same url used when subscribing. Required.
  @param mode              verification mode. Required.
  @param verificationToken verification token to be echoed back to the subscriber during the
  verification callback. Optional.
  @return if successful, response.stat will be "ok".
  @throws JinxException if required parameters are missing, or if there are any errors.
  @see <a href="https://www.flickr.com/services/api/flickr.push.unsubscribe.html">flickr.push.unsubscribe</a>