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

def default_config(self):
        c = Config({
            'CSSHTMLHeaderPreprocessor': {
                'enabled': False
            },
            'VoilaExporter': {
                'markdown_renderer_class': 'voila.exporter.VoilaMarkdownRenderer'
            }
        })
        c.merge(super(VoilaExporter, self).default_config)
        return c

resources = {
            'base_url': self.base_url,
            'nbextensions': nbextensions,
            'theme': self.voila_configuration.theme
        }

        # include potential extra resources
        extra_resources = self.voila_configuration.config.VoilaConfiguration.resources
        # if no resources get configured from neither the CLI nor a config file,
        # extra_resources is a traitlets.config.loader.LazyConfigValue object
        if not isinstance(extra_resources, dict):
            extra_resources = extra_resources.to_dict()
        if extra_resources:
            recursive_update(resources, extra_resources)

        self.exporter = VoilaExporter(
            template_path=self.nbconvert_template_paths,
            config=self.traitlet_config,
            contents_manager=self.contents_manager  # for the image inlining
        )
        if self.voila_configuration.strip_sources:
            self.exporter.exclude_input = True
            self.exporter.exclude_output_prompt = True
            self.exporter.exclude_input_prompt = True

        # These functions allow the start of a kernel and execution of the notebook after (parts of) the template
        # has been rendered and send to the client to allow progressive rendering.
        # Template should first call kernel_start, and then decide to use notebook_execute
        # or cell_generator to implement progressive cell rendering
        extra_context = {
            # NOTE: we can remove the lambda is we use jinja's async feature, which will automatically await the future
            'kernel_start': lambda: self._jinja_kernel_start().result(),  # pass the result (not the future) to the template

)
    aliases = {
        'port': 'Voila.port',
        'static': 'Voila.static_root',
        'strip_sources': 'VoilaConfiguration.strip_sources',
        'autoreload': 'Voila.autoreload',
        'template': 'VoilaConfiguration.template',
        'theme': 'VoilaConfiguration.theme',
        'base_url': 'Voila.base_url',
        'server_url': 'Voila.server_url',
        'enable_nbextensions': 'VoilaConfiguration.enable_nbextensions'
    }
    classes = [
        VoilaConfiguration,
        VoilaExecutePreprocessor,
        VoilaExporter,
        VoilaCSSPreprocessor
    ]
    connection_dir_root = Unicode(
        config=True,
        help=_(
            'Location of temporry connection files. Defaults '
            'to system `tempfile.gettempdir()` value.'
        )
    )
    connection_dir = Unicode()

    base_url = Unicode(
        '/',
        config=True,
        help=_(
            'Path for voila API calls. If server_url is unset, this will be \