code: public Topics getList(String groupId, int perPage, int page, boolean sign) throws JinxException {
      JinxUtils.validateParams(groupId);
      Map<String, String> params = new TreeMap<>();
      params.put("method", "flickr.groups.discuss.topics.getList");
      params.put("group_id", groupId);
      if (perPage > 0) {
        params.put("per_page", Integer.toString(perPage));
      }
      if (page > 0) {
        params.put("page", Integer.toString(page));
      }
      return jinx.flickrGet(params, Topics.class, sign);
    }
docs: Get a list of discussion topics in a group.
  <br>
  This method does not require authentication. Unsigned requests can only see public topics.
  
  @param groupId (Required) The NSID of the group to fetch information for.
  @param perPage Number of photos to return per page. If this argument is less than 1, it defaults to 100.
  The maximum allowed value is 500.
  @param page    The page of results to return. If this argument is less than 1, it defaults to 1.
  @param sign    if true, the request will be signed.
  @return object with topic metadata and a list of topics.
  @throws JinxException if required parameters are missing, or if there are any errors.
  @see <a href="https://www.flickr.com/services/api/flickr.groups.discuss.topics.getList.html">flickr.groups.discuss.topics.getList</a>