@Override public void process(BufferedWriter writer) throws Exception {
        for (Map.Entry<String, Collection<String>> entry : groups.entrySet()) {
          writer.write(entry.getKey());
          writer.write(':');
          writer.newLine();
          for (String name : entry.getValue()) {
            writer.write("  ");
            writer.write(name);
            writer.newLine();
          }
        }
      }
@Override public void process(BufferedWriter writer)