public function content($parentView = null)
    {
        if ($parentView === null) {
            $content                 = ob_get_clean();
            ob_clean();
            $this->params['scripts'] = $this->generateScripts();
            $this->params['css']     = $this->generateCSS();
            echo $this->render($this->parentLayout,
                array_merge($this->getBlocks(), $this->params,
                    ['content' => $content])
            );
        } else {
            $this->parentLayout = $parentView;
            ob_start();
        }
    }