docs: public static void mergeHints(InputStream is, Map<String,List<Long>> hints) throws IOException {
      final BufferedReader reader = new BufferedReader(
          new InputStreamReader(is, Charsets.UTF_8));
      
      String line;
      while ((line = reader.readLine()) != null) {
        line = line.trim();
        if (line.isEmpty() || line.startsWith("#"))
          continue;
  
        final int equals = line.indexOf('=');
        if (equals <= 0) {
          throw new IOException("No '=' character on a non-comment line?: " + line);
        } else {
          String key = line.substring(0, equals);
          List<Long> values = hints.get(key);
          if (values == null) {
            hints.put(key, values = new ArrayList<>());
          }
          for (String v : line.substring(equals + 1).split("[\\,]")) {
            if (!v.isEmpty()) values.add(Long.parseLong(v));
          }
        }
      }
    }