code: function(name) {
        var loader = this._loader;
        if (loader.modules[name])
          return Promise.resolve();
        return loader.importPromises[name] || createImportPromise(this, name, new Promise(asyncStartLoadPartwayThrough({
          step: 'locate',
          loader: loader,
          moduleName: name,
          moduleMetadata: {},
          moduleSource: undefined,
          moduleAddress: undefined
        }))
        .then(function() {
          delete loader.importPromises[name];
        }));
      }
docs: 26.3.3.9 keys not implemented 26.3.3.10