How to use the hexo-front-matter.split function in hexo-front-matter

module.exports = function (model, id, update, callback, hexo) {
  function removeExtname(str) {
    return str.substring(0, str.length - path.extname(str).length);
  }
  var post = hexo.model(model).get(id)
  if (!post) {
    return callback('Post not found');
  }
  var config = hexo.config,
    slug = post.slug = hfm.escape(post.slug || post.title, config.filename_case),
    layout = post.layout = (post.layout || config.default_layout).toLowerCase(),
    date = post.date = post.date ? moment(post.date) : moment();

  var split = hfm.split(post.raw),
    frontMatter = split.data
    compiled = hfm.parse([frontMatter, '---', split.content].join('\n'));

  var preservedKeys = ['title', 'date', 'tags', 'categories', '_content', 'author'];
  Object.keys(hexo.config.metadata || {}).forEach(function (key) {
    preservedKeys.push(key);
  });
  var prev_full = post.full_source,
    full_source = prev_full;
  if (update.source && update.source !== post.source) {
    // post.full_source only readable ~ see: /hexo/lib/models/post.js
    full_source = hexo.source_dir + update.source
  }

  preservedKeys.forEach(function (attr) {
    if (attr in update) {

module.exports = function (model, id, update, callback, hexo) {
  var post = hexo.model(model).get(id)
  if (!post) {
    return callback('Post not found');
  }
  var config = hexo.config,
    slug = post.slug = hfm.escape(post.slug || post.title, config.filename_case),
    layout = post.layout = (post.layout || config.default_layout).toLowerCase(),
    date = post.date = post.date ? moment(post.date) : moment();

  var split = hfm.split(post.raw),
    frontMatter = split.data
    compiled = hfm.parse([frontMatter, '---', split.content].join('\n'));

  var preservedKeys = ['title', 'date', 'tags', 'categories', '_content', 'keywords', 'description'];
  var prev_full = post.full_source,
    full_source = prev_full;
  if (update.source && update.source !== post.source) {
    // post.full_source only readable ~ see: /hexo/lib/models/post.js
    full_source = hexo.source_dir + update.source
  }

  preservedKeys.forEach(function (attr) {
    if (attr in update) {
      compiled[attr] = update[attr]
    }
  });

return this._getScaffold(data.layout).then(scaffold => {
    const frontMatter = prepareFrontMatter({...data});
    yfmSplit = yfm.split(scaffold);

    return tag.render(yfmSplit.data, frontMatter);
  }).then(frontMatter => {
    const { separator } = yfmSplit;

raw(query) {
        let post = this.detail(query);
        if (!post) return null;
        return hfm.split(post.raw);
    }