code: function getStylingNodes (selector) {
      if (typeof queryCache[selector] === 'undefined') {
        queryCache[selector] = Array.prototype.map.call(
          document.querySelectorAll(selector),
          function (stylesheet) {
            return stylesheet.outerHTML;
          }
        ).join('');
      }
  
      return queryCache[selector];
    }
docs: Get the styling nodes to inject in the head of the embedded document
  
  @param  {String} selector
  @return {String}