code: public function getConfigTreeBuilder()
      {
          $treeBuilder = new TreeBuilder();
          $rootNode    = $treeBuilder->root('metamodels');
  
          $rootNode
              ->children()
                  ->booleanNode('enable_cache')
                      ->defaultValue(!$this->debug)
                  ->end()
                  ->scalarNode('cache_dir')
                      ->defaultValue('%kernel.cache_dir%' . DIRECTORY_SEPARATOR . 'metamodels')
                  ->end()
                  ->scalarNode('assets_dir')
                      ->cannotBeEmpty()
                      ->defaultValue($this->resolvePath($this->rootDir . '/assets/metamodels'))
                      ->validate()
                          ->always(function ($value) {
                              return $this->resolvePath($value);
                          })
                      ->end()
                  ->end()
                  ->scalarNode('assets_web')
                      ->cannotBeEmpty()
                      ->defaultValue('assets/metamodels')
                  ->end()
              ->end();
  
          return $treeBuilder;
      }
docs: Generates the configuration tree builder.
  
  @return TreeBuilder