docs: private Pair<Map<String, Frame>, Map<String, Set<String>>> fetchFrames() {
      Map<String, Frame> all_frames = null;
      Map<String, Set<String>> all_frames_cols = null;
  
      if (this.find_compatible_frames) {
        // caches for this request
        all_frames = Frames.fetchAll();
        all_frames_cols = new TreeMap<String, Set<String>>();
  
        for (Map.Entry<String, Frame> entry : all_frames.entrySet()) {
          all_frames_cols.put(entry.getKey(), new TreeSet<String>(Arrays.asList(entry.getValue()._names)));
        }
      }
      return new Pair<Map<String, Frame>, Map<String, Set<String>>>(all_frames, all_frames_cols);
    }