code: public Observable<Void> deleteUserAsync(String poolId, String nodeId, String userName) {
          return deleteUserWithServiceResponseAsync(poolId, nodeId, userName).map(new Func1<ServiceResponseWithHeaders<Void, ComputeNodeDeleteUserHeaders>, Void>() {
              @Override
              public Void call(ServiceResponseWithHeaders<Void, ComputeNodeDeleteUserHeaders> response) {
                  return response.body();
              }
          });
      }
docs: Deletes a user account from the specified compute node.
  You can delete a user account to a node only when it is in the idle or running state.
  
  @param poolId The ID of the pool that contains the compute node.
  @param nodeId The ID of the machine on which you want to delete a user account.
  @param userName The name of the user account to delete.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceResponseWithHeaders} object if successful.