How to use the voila.exporter.VoilaMarkdownRenderer function in voila

def image(self, src, title, text):
        contents_manager = self.options['contents_manager']
        if contents_manager.file_exists(src):
            content = contents_manager.get(src, format='base64')
            data = content['content'].replace('\n', '')  # remove the newline
            mime_type, encoding = mimetypes.guess_type(src)
            src = 'data:{mime_type};base64,{data}'.format(mime_type=mime_type, data=data)
        return super(VoilaMarkdownRenderer, self).image(src, title, text)