code: function (dirs, done) {
      var self = this;
      var loader = new Loader();
      loader.collectExtensions(dirs, function (err) {
        if (err) return done(err);
        loader.initWorkerExtensions({}, function (err, extensions) {
          if (err) return done(err);
          self.extensions = extensions;
          done(null);
        });
      });
    }
docs: public API