code: public function getConfigTreeBuilder()
      {
          $treeBuilder = new TreeBuilder();
          $rootNode = $treeBuilder->root('chill_custom_fields');
          
          $classInfo = "The class which may receive custom fields";
          $nameInfo = "The name which will appears in the user interface. May be translatable";
          $optionsInfo = "Options available for custom fields groups referencing this class";
          $optionsFormType = "The name of the form to append";
          $optionsFormOptionsInfos = "the arguments to pass the form";
          $customizableEntitiesInfo = "A list of customizable entities";
  
          $rootNode
              ->children()
                  ->arrayNode('customizables_entities')
                      ->info($customizableEntitiesInfo)
                      ->defaultValue(array())
                      ->prototype('array')
                      ->children()
                          ->scalarNode('class')->isRequired()->info($classInfo)
                          ->end()
                          ->scalarNode('name') ->isRequired()->info($nameInfo)
                          ->end()
                          ->arrayNode('options')
                              ->info($optionsInfo)
                              ->defaultValue(array())
                              ->useAttributeAsKey('key')
                              ->prototype('array')
                                  ->children()
                                      ->scalarNode('form_type')
                                          ->isRequired()
                                          ->info($optionsFormType)
                                      ->end()
                                      ->variableNode('form_options')
                                          ->info($optionsFormOptionsInfos)
                                          ->defaultValue(array())
                                      ->end()
                                  ->end()
                              ->end()
                          ->end()
                      ->end()
                  ->end()
              ->end()
              ->booleanNode('show_empty_values_in_views')
                  ->info('Show the empty value for custom fields in the views, timeline, ...')
                  ->defaultValue(true)
              ->end()
          ->end()
          ;
  
          return $treeBuilder;
      }
docs: {@inheritDoc}