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

        $classDefinition = $rootNode
            ->children()
                ->arrayNode('classes')
                    ->prototype('array')
                        ->children();

        $this->appendClassDefinition($classDefinition);

        $classDefinition->end()
                    ->end()
                ->end()
            ->end();

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

        $classDefinition = $rootNode
            ->children()
                ->arrayNode('classes')
                    ->prototype('array')
                        ->children();

        $this->appendClassDefinition($classDefinition);

        $classDefinition->end()
                    ->end()
                ->end()
            ->end();

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