code: public function checkFramework($value)
  	{
  		if (empty($value))
  		{
  			return '';
  		}
  
  		$array = Contao\StringUtil::deserialize($value);
  
  		if (empty($array) || !\is_array($array))
  		{
  			return $value;
  		}
  
  		if (($i = array_search('responsive.css', $array)) !== false && !\in_array('layout.css', $array))
  		{
  			array_insert($array, $i, 'layout.css');
  		}
  
  		return $array;
  	}
docs: Auto-select layout.css if responsive.css is selected (see #8222)
  
  @param mixed $value
  
  @return string