code: public Observable<Void> rebootAsync(String poolId, String nodeId) {
          return rebootWithServiceResponseAsync(poolId, nodeId).map(new Func1<ServiceResponseWithHeaders<Void, ComputeNodeRebootHeaders>, Void>() {
              @Override
              public Void call(ServiceResponseWithHeaders<Void, ComputeNodeRebootHeaders> response) {
                  return response.body();
              }
          });
      }
docs: Restarts the specified compute node.
  You can restart a node only if it is in an idle or running state.
  
  @param poolId The ID of the pool that contains the compute node.
  @param nodeId The ID of the compute node that you want to restart.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceResponseWithHeaders} object if successful.