code: public function prepend(ContainerBuilder $container)
      {
          $cacheConfig    = array();
          $doctrineConfig = array();
  
          $cacheConfig['providers']['contentful_api_cache'] = array(
              'namespace'   => 'contentful_api',
              'type'        => 'file_system',
              'file_system' => array(
                  'directory' => '%kernel.root_dir%/cache/contentful'
              )
          );
          $cacheConfig['providers']['contentful_lastmodified_cache'] = array(
              'namespace'   => 'contentful_lastmodified_cache',
              'type'        => 'file_system',
              'file_system' => array(
                  'directory' => '%kernel.root_dir%/cache/contentful'
              )
          );
          $container->prependExtensionConfig('doctrine_cache', $cacheConfig);
  
          $doctrineConfig['orm']['mappings']['contentful_bundle'] = array(
              'type'   => 'annotation',
              'alias'  => 'ContentfulBundle',
              'dir'    => __DIR__ . '/../Item',
              'prefix' => 'Dothiv\Bundle\ContentfulBundle\Item'
          );
          $container->prependExtensionConfig('doctrine', $doctrineConfig);
      }
docs: Allow an extension to prepend the extension configurations.
  
  @param ContainerBuilder $container