code: public UserUrls getUserPhotos(String userId) throws JinxException {
      Map<String, String> params = new TreeMap<>();
      params.put("method", "flickr.urls.getUserPhotos");
      if (!JinxUtils.isNullOrEmpty(userId)) {
        params.put("user_id", userId);
      }
      return jinx.flickrGet(params, UserUrls.class);
    }
docs: Returns the url to a user's photos.
  
  This method does not require authentication.
  
  @param userId user id (NSID) of the user to fetch the url for. If omitted, the calling user is assumed. Optional.
  @return user id and rl to the users photos.
  @throws JinxException if there are any errors.
  @see <a href="https://www.flickr.com/services/api/flickr.urls.getUserPhotos.html">flickr.urls.getUserPhotos</a>