How to use the hexo-util.gravatar function in hexo-util

return post.draft !== true;
  });

  if (posts.length <= 0) {
    feedConfig.autodiscovery = false;
    return;
  }

  if (feedConfig.limit) posts = posts.limit(feedConfig.limit);

  let url = config.url;
  if (url[url.length - 1] !== '/') url += '/';

  let icon = '';
  if (feedConfig.icon) icon = full_url_for.call(this, feedConfig.icon);
  else if (config.email) icon = gravatar(config.email);

  const xml = template.render({
    config,
    url,
    icon,
    posts,
    feed_url: config.root + path
  });

  return {
    path,
    data: xml
  };
};

function getAvatar() {
        if (gravatar) {
            return gravatrHelper(gravatar, 128);
        }
        if (avatar) {
            return url_for(avatar);
        }
        return url_for('/img/avatar.png');
    }

module.exports = function(email, options) {
  return gravatar(email, options);
};