code: public function getConfigTreeBuilder()
      {
          $treeBuilder = new TreeBuilder();
          $rootNode = $treeBuilder->root('c33s_contact_form');
          
          $rootNode
  	    ->children()
  		->arrayNode('email')
  		    ->canBeEnabled()
  		    ->children()
  			->scalarNode('subject')
  			    ->isRequired()
  			    ->cannotBeEmpty()
  			->end()
  			->scalarNode('sender_email')
  			    ->isRequired()
  			    ->cannotBeEmpty()
  			->end()
  			->arrayNode('recipients')
  			    ->defaultValue(array())
  			    ->useAttributeAsKey('email')
  			    ->prototype('scalar')
  				->isRequired()
  				->cannotBeEmpty()
  			    ->end()
  			->end()
  			->booleanNode('send_copy_to_user')
  			    ->defaultValue(false)
  			->end()
  		    ->end()
  		->end()
  		->arrayNode('database')
  		    ->canBeEnabled()
  		->end()
  	    ->end()
  	;
          
          return $treeBuilder;
      }
docs: {@inheritDoc}