async genImageIframeSsrLite(prompt, messageId, onProgress) {
    const { pollingUrl } = await this.genImagePage(prompt, messageId)
    const resultHtml = await this.pollingImgRequest(pollingUrl, onProgress)
    return this.createImageIframe(resultHtml, true)
  }
Create a server side render iframe which uses 'srcdoc' attribute to hold the rendered result page.
Unlike genImageIframeSsr, it returns an iframe that only contains the content of the image result page.
@param {string} prompt - The prompt for the image generation. It should be given by 'Sydney'.
@param {string} messageId - The message ID refers to the message of 'Sydney'.
@param {function({BicProgressContext}):boolean} onProgress - A callback function that will be invoked intervally during the image generation.
                                                             Return true to cancel creation.
@returns {string} The html string of the iframe created.