code: public GroupUrls lookupGroup(String url) throws JinxException {
      JinxUtils.validateParams(url);
      Map<String, String> params = new TreeMap<>();
      params.put("method", "flickr.urls.lookupGroup");
      params.put("url", url);
      return jinx.flickrGet(params, GroupUrls.class, false);
    }
docs: Returns a group NSID, given the url to a group's page or photo pool.
  
  This method does not require authentication.
  
  @param url url to the group's page or photo pool. Required.
  @return group NSID and name.
  @throws JinxException if the url is missing, or if there are any errors.
  @see <a href="https://www.flickr.com/services/api/flickr.urls.lookupGroup.html">flickr.urls.lookupGroup</a>