docs: function Renderer(options) {
    if (!(this instanceof Renderer)) {
      return new Renderer(options);
    }
  
    // create complete options object (using defaults)
    if (options) {
      debug("creating koa-handlebars instance with options", options);
    } else {
      debug("creating koa-handlebars instance");
    }
  
    var o = this.options = extend({}, Renderer.defaults, options);
    debug("using %s as the root", chalk.grey(o.root));
  
    // custom handlebars instance
    if (o.handlebars) {
      debug("using a custom handlebars instance");
      this.handlebars = o.handlebars;
    } else {
      this.handlebars = handlebars.create();
    }
  
    // register global helpers/partials
    if (o.helpers) this.helper(o.helpers);
    if (o.partials) this.partial(o.partials);
  
    // enabling caching (via lru-cache)
    if (o.cache) {
      debug("caching enabled");
      this.cache = new Cache({ max: 100 });
    }
  }