private function createStylesheetConstraint($attibutes, $tag, $class)
 {
     $constraint = new StylesheetConstraint($attibutes);
     $constraint->setTag($tag);
     $constraint->addClass($class);
     return $constraint;
 }
 private function createContainer(array $attributes = array(), array $complexAttributes = array(), array $classes = array())
 {
     $constraint = new StylesheetConstraint(array_merge($attributes, $complexAttributes));
     foreach ($classes as $class) {
         $constraint->addClass($class);
     }
     return $constraint;
 }