code: public Observable<Void> stopResizeAsync(String poolId) {
          return stopResizeWithServiceResponseAsync(poolId).map(new Func1<ServiceResponseWithHeaders<Void, PoolStopResizeHeaders>, Void>() {
              @Override
              public Void call(ServiceResponseWithHeaders<Void, PoolStopResizeHeaders> response) {
                  return response.body();
              }
          });
      }
docs: Stops an ongoing resize operation on the pool.
  This does not restore the pool to its previous state before the resize operation: it only stops any further changes being made, and the pool maintains its current state. After stopping, the pool stabilizes at the number of nodes it was at when the stop operation was done. During the stop operation, the pool allocation state changes first to stopping and then to steady. A resize operation need not be an explicit resize pool request; this API can also be used to halt the initial sizing of the pool when it is created.
  
  @param poolId The ID of the pool whose resizing you want to stop.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceResponseWithHeaders} object if successful.