code: @Override
      public CancelUpdateStackResult cancelUpdateStack(CancelUpdateStackRequest request) {
          request = beforeClientExecution(request);
          return executeCancelUpdateStack(request);
      }
docs: <p>
  Cancels an update on the specified stack. If the call completes successfully, the stack rolls back the update and
  reverts to the previous stack configuration.
  </p>
  <note>
  <p>
  You can cancel only stacks that are in the UPDATE_IN_PROGRESS state.
  </p>
  </note>
  
  @param cancelUpdateStackRequest
  The input for the <a>CancelUpdateStack</a> action.
  @return Result of the CancelUpdateStack operation returned by the service.
  @throws TokenAlreadyExistsException
  A client request token already exists.
  @sample AmazonCloudFormation.CancelUpdateStack
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/cloudformation-2010-05-15/CancelUpdateStack"
  target="_top">AWS API Documentation</a>