public function getConfigTreeBuilder()
{
$treeBuilder = new TreeBuilder();
$node = $treeBuilder->root('sonata_delivery');
$node->children()->scalarNode('selector')->defaultValue('sonata.delivery.selector.default')->cannotBeEmpty()->end()->end();
$this->addDeliverySection($node);
$this->addModelSection($node);
return $treeBuilder;
}