docs: @SuppressWarnings("unchecked")
    private HashMap<String, Object> loadCachedJson(final HttpQuery query,
                                         final long end_time,
                                         final long max_age,
                                         final String basepath)
                                         throws JsonParseException,
                                         JsonMappingException, IOException {
      final String json_path = basepath + ".json";
      File json_cache = new File(json_path);
      if (staleCacheFile(query, end_time, max_age, json_cache)) {
        return null;
      }
      final byte[] json = readFile(query, json_cache, 4096);
      if (json == null) {
        return null;
      }
      json_cache = null;
  
      return (HashMap<String, Object>) JSON.parseToObject(json, HashMap.class);
    }