code: public static void print(Message message, Appendable output) throws IOException {
          JsonGenerator generator = new JsonGenerator(output);
          generator.print("{");
          print(message, generator);
          generator.print("}");
      }
docs: Outputs a textual representation of the Protocol Message supplied into the parameter output.
  (This representation is the new version of the classic "ProtocolPrinter" output from the
  original Protocol Buffer system)