public function css($file, $options = [])
    {
        $file = $this->_addExt($file, '.css');
        if (!$this->collection()->contains($file)) {
            throw new RuntimeException(
                "Cannot create a stylesheet tag for a '$file'. That build is not defined."
            );
        }
        $output = '';
        if (!empty($options['raw'])) {
            unset($options['raw']);
            $target = $this->collection()->get($file);
            foreach ($target->files() as $part) {
                $path = $this->_relativizePath($part->path());
                if (DS === '\\') {
                    $path = str_replace(DS, '/', $path);
                }
                $output .= $this->Html->css($path, $options);
            }

            return $output;
        }

        $url = $this->url($file, $options);
        unset($options['full']);

        return $this->Html->css($url, $options);
    }