if (!file_exists($path . $filename)) {
        $cache_file = FALSE;
        // Allow modules to override the cache building
        foreach (module_implements('_build_css_cache') as $module) {
          $function = $module .'_build_css_cache';
          $cache_file = $function($types, $filename);
        }
        if ($cache_file === FALSE) {
          drupal_build_css_cache($types, $filename);
          $cache_file = base_path() . $path . $filename;
        }
      }