code: public PhotoList<Photo> getPhotos(String groupId, String[] tags, Set<String> extras, int perPage, int page) throws FlickrException {
          return getPhotos(groupId, null, tags, extras, perPage, page);
      }
docs: Convenience/Compatibility method.
  
  This method does not require authentication.
  
  @see com.flickr4java.flickr.photos.Extras
  @param groupId
  The group ID
  @param tags
  The optional tags (may be null)
  @param extras
  Set of extra-attributes to include (may be null)
  @param perPage
  The number of photos per page (0 to ignore)
  @param page
  The page offset (0 to ignore)
  @return A Collection of Photo objects
  @throws FlickrException