private function addSelect2(ArrayNodeDefinition $rootNode)
    {
        $rootNode
            ->children()
                ->arrayNode('select2')
                    ->canBeUnset()
                    ->treatNullLike(['enabled' => true])
                    ->treatTrueLike(['enabled' => true])
                    ->addDefaultsIfNotSet()
                    ->children()
                        ->booleanNode('enabled')->defaultTrue()->end()
                    ->end()
                ->end()
                ->arrayNode('datetime_picker')
                    ->canBeUnset()
                    ->treatNullLike(['enabled' => true])
                    ->treatTrueLike(['enabled' => true])
                    ->addDefaultsIfNotSet()
                    ->children()
                        ->booleanNode('enabled')->defaultTrue()->end()
                    ->end()
                ->end()
            ->end()
        ;
    }