code: public ImmutableList<SoyMsgPart> getSoyMsgParts(
        long msgId, ImmutableList<SoyMsgPart> defaultMsgParts) {
      ImmutableList<SoyMsgPart> msgParts = msgBundle.getMsgParts(msgId);
      if (msgParts.isEmpty()) {
        return defaultMsgParts;
      }
      return msgParts;
    }
docs: Returns the {@link SoyMsg} associated with the {@code msgId} or the fallback (aka english)
  translation if there is no such message.