docs: public static void writeHints(File file, Map<String,List<Long>> hints) throws IOException {
      Closer closer = Closer.create();
      try {
        BufferedWriter w = closer.register(Files.newWriter(file, Charsets.UTF_8));
        if (!(hints instanceof SortedMap)) {
          hints = new TreeMap<String,List<Long>>(hints);
        }
        
        Joiner joiner = Joiner.on(',');
        for (Map.Entry<String,List<Long>> e : hints.entrySet()) {
          w.write(e.getKey());
          w.write("=");
          joiner.appendTo(w, e.getValue());
          w.write("\n");
        }
      } catch (Throwable t) {
        throw closer.rethrow(t);
      } finally {
        closer.close();
      }
    }