parseLandmarks(navHtml) {
    var navElement = Object(core["querySelectorByType"])(navHtml, "nav", "landmarks");
    var navItems = navElement ? Object(core["qsa"])(navElement, "li") : [];
    var length = navItems.length;
    var i;
    var list = [];
    var item;
    if (!navItems || length === 0) return list;

    for (i = 0; i < length; ++i) {
      item = this.landmarkItem(navItems[i]);

      if (item) {
        list.push(item);
        this.landmarksByType[item.type] = i;
      }
    }

    return list;
  }
Parse landmarks from a Epub > 3.0 Nav
@private
@param  {document} navHtml
@return {array} landmarks list