code: 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;
  }
docs: Conditionally cache `compiled` template based
  on the `options` filename and `.cache` boolean.
  
  @param {Object} options
  @param {Function} compiled
  @return {Function}
  @api private