code: private static long computeMsgIdUsingBracedPhs(MsgNode msgNode) {
      return SoyMsgIdComputer.computeMsgIdUsingBracedPhs(
          buildMsgParts(msgNode), msgNode.getMeaning(), msgNode.getContentType());
    }
docs: Computes the alternate unique id for this message. Only use this if you use braced
  placeholders.
  
  @param msgNode The message parsed from the Soy source.
  @return The alternate message id using braced placeholders.