@omneedia/socketcluster/sample/node_modules/rxjs/add/operator/groupBy.d.ts

SocketCluster - A Highly parallelized WebSocket server cluster to make the most of multi-core machines/instances.

import { groupBy } from '../../operator/groupBy';
declare module '../../Observable' {
    interface Observable<T> {
        groupBy: typeof groupBy;
    }
}