() => {

				var stream = fromEvent( document, "mousemove" ).pipe(
					// While the mouse-events are being triggered continuously on the
					// document (while the user is mousing-around), we only want to let
					// one event through every few seconds.
					throttleTime( 2000 ),
					map(
						( event: MouseEvent ) : MousePosition => {

							return({
								viewport: {
									x: event.clientX,
									y: event.clientY
								},
								document: {
									x: event.pageX,
									y: event.pageY
								}
							});

						}
					)
				);

				return( stream );

			}

  it('should throttle values until source raises error', () => {
    const e1 =   hot('-a--(bc)-------d---------------#');
    const subs =     '^                              !';
    const expected = '-a-------------d---------------#';

    expectObservable(e1.pipe(throttleTime(50, rxTestScheduler))).toBe(expected);
    expectSubscriptions(e1.subscriptions).toBe(subs);
  });

export const limitMessageRateEpic: Epic<ActionOf<any>, ActionOf<any>, StoreState, EpicDependencies> = action$ => {
  return action$.ofType(limitMessageRatePayloadAction.type).pipe(
    throttleTime(1),
    map((action: ActionOf<LimitMessageRatePayload>) => {
      const { exploreId, data, dataReceivedActionCreator } = action.payload;
      return dataReceivedActionCreator({ exploreId, data });
    })
  );
};

  getContacts() {
    return this.contactsApiClient.getContacts().valueChanges().pipe(map((users: User[]) => {
      return users.filter((user: User) => {
        return user.uid !== this.authService.getUid();
      });
    }))

    .pipe(throttleTime(5000)) as Observable<User[]>;
  }