docs: function cache(options, compiled) {
    // cachable
    if (compiled && options.filename && options.cache) {
      delete templates[options.filename];
      cacheStore[options.filename] = compiled;
      return compiled;
    }
    // check cache
    if (options.filename && options.cache) {
      return cacheStore[options.filename];
    }
    return compiled;
  }