How to use the messaging-api-line.Line.createFlex function in messaging-api-line

replyFlex(
    altText: string,
    flex: LineTypes.FlexContainer,
    options?: LineTypes.MessageOptions
  ) {
    return this.reply([Line.createFlex(altText, flex, options)], options);
  }

sendFlex(
    altText: string,
    flex: LineTypes.FlexContainer,
    options?: LineTypes.MessageOptions
  ) {
    return this.send([Line.createFlex(altText, flex, options)], options);
  }

pushFlex(
    altText: string,
    flex: LineTypes.FlexContainer,
    options?: LineTypes.MessageOptions
  ) {
    return this.push([Line.createFlex(altText, flex, options)], options);
  }