code: public function prepend(ContainerBuilder $container)
      {
          // Generate a config array with the content of `liip_theme.yml` file
          $liipThemeConfig = Yaml::parse(file_get_contents(dirname(__DIR__) . '/Resources/config/liip_theme.yaml'));
  
          // Set available themes
          $liipThemeConfig['liip_theme']['themes'] = array_keys($container->getParameter('kernel.themes'));
  
          // Prepend the `liip_theme` settings
          $container->prependExtensionConfig('liip_theme', $liipThemeConfig['liip_theme']);
  
          // get all bundles
          $bundles = $container->getParameter('kernel.bundles');
  
          if (isset($bundles['HarmonySettingsManagerBundle'])) {
              // Generate a config array with the content of `settings_manager.yml` file
              $settings = Yaml::parse(file_get_contents(dirname(__DIR__) . '/Resources/config/settings_manager.yaml'));
  
              // Prepend the `harmony_settings_manager` settings
              $container->prependExtensionConfig('harmony_settings_manager', $settings['harmony_settings_manager']);
          }
      }
docs: Allow an extension to prepend the extension configurations.
  
  @param ContainerBuilder $container
  
  @throws Exception