DependencyInjection/Configuration.php
public function getConfigTreeBuilder()
    {
        $treeBuilder = new TreeBuilder();
        $rootNode = $treeBuilder->root($this->root);

        $resourceDefinition = $rootNode
            ->children()
            ->arrayNode('configurations')
            ->useAttributeAsKey('code')
            ->prototype('array')
            ->performNoDeepMerging()
            ->children();

        $this->appendResourceDefinition($resourceDefinition);

        $resourceDefinition->end()
            ->end()
            ->end()
            ->end();

        return $treeBuilder;
    }
public function getConfigTreeBuilder()
    {
        $treeBuilder = new TreeBuilder();
        $rootNode = $treeBuilder->root($this->root);

        $resourceDefinition = $rootNode
            ->children()
            ->arrayNode('configurations')
            ->useAttributeAsKey('code')
            ->prototype('array')
            ->performNoDeepMerging()
            ->children();

        $this->appendResourceDefinition($resourceDefinition);

        $resourceDefinition->end()
            ->end()
            ->end()
            ->end();

        return $treeBuilder;
    }
{@inheritdoc}
@throws \RuntimeException