docs: function(deck) {
    var hasDataMarkdownAttribute,
        elements = [];
  
    elements.push(deck.parent);
    deck.slides.forEach(function(slide) {
      elements.push(slide);
    });
    hasDataMarkdownAttribute = elements.some(function(current) {
      return current.getAttribute('data-markdown') !== null;
    });
  
    return hasDataMarkdownAttribute ? 'transform-marked-elements-only' :
      'transform-content-of-all-slides';
  }