code: function(text, base, map) {
      var matches = this.loader.extractUrls(text, base);
      var match, url, intermediate;
      for (var i = 0; i < matches.length; i++) {
        match = matches[i];
        url = match.url;
        // resolve any css text to be relative to the importer, keep absolute url
        intermediate = urlResolver.resolveCssText(map[url], url, true);
        // flatten intermediate @imports
        intermediate = this.flatten(intermediate, base, map);
        text = text.replace(match.matched, intermediate);
      }
      return text;
    }
docs: flatten all the @imports to text