PizzaSize: {
  publishPromptMessage: async (event, context) => {
    context.getLogger().info(context.getCurrentItem() + " : publishPromptMessage");
    let promptCount = event.promptCount;
    if (promptCount > 0) {
      //add error message
      let candidateMessages = context.getCandidateMessages();
      let errorMessage = "Your provided message '" + context.getUserInput() +
                         "' is not a valid pizza size. "
      candidateMessages[0].text = errorMessage + candidateMessages[0].text;
      context.addCandidateMessages(candidateMessages);
    }
    else {
      context.addCandidateMessages(context.getCandidateMessages());
    }
  }
}