code: @Override
      public ReservedNode purchaseReservedNodeOffering(PurchaseReservedNodeOfferingRequest request) {
          request = beforeClientExecution(request);
          return executePurchaseReservedNodeOffering(request);
      }
docs: <p>
  Allows you to purchase reserved nodes. Amazon Redshift offers a predefined set of reserved node offerings. You
  can purchase one or more of the offerings. You can call the <a>DescribeReservedNodeOfferings</a> API to obtain
  the available reserved node offerings. You can call this API by providing a specific reserved node offering and
  the number of nodes you want to reserve.
  </p>
  <p>
  For more information about reserved node offerings, go to <a
  href="https://docs.aws.amazon.com/redshift/latest/mgmt/purchase-reserved-node-instance.html">Purchasing Reserved
  Nodes</a> in the <i>Amazon Redshift Cluster Management Guide</i>.
  </p>
  
  @param purchaseReservedNodeOfferingRequest
  @return Result of the PurchaseReservedNodeOffering operation returned by the service.
  @throws ReservedNodeOfferingNotFoundException
  Specified offering does not exist.
  @throws ReservedNodeAlreadyExistsException
  User already has a reservation with the given identifier.
  @throws ReservedNodeQuotaExceededException
  Request would exceed the user's compute node quota. For information about increasing your quota, go to <a
  href="https://docs.aws.amazon.com/redshift/latest/mgmt/amazon-redshift-limits.html">Limits in Amazon
  Redshift</a> in the <i>Amazon Redshift Cluster Management Guide</i>.
  @throws UnsupportedOperationException
  The requested operation isn't supported.
  @sample AmazonRedshift.PurchaseReservedNodeOffering
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/redshift-2012-12-01/PurchaseReservedNodeOffering"
  target="_top">AWS API Documentation</a>