private function addMonologSection(ArrayNodeDefinition $rootNode)
    {
        $rootNode
            ->children()
                ->arrayNode('monolog')
                    ->canBeUnset()
                    ->children()
                        ->scalarNode('client')->isRequired()->end()
                        ->scalarNode('key')->isRequired()->end()
                        ->scalarNode('formatter')->end()
                    ->end()
                ->end()
            ->end();
    }