code: @Override
      public ValidDBInstanceModificationsMessage describeValidDBInstanceModifications(DescribeValidDBInstanceModificationsRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeValidDBInstanceModifications(request);
      }
docs: <p>
  You can call <a>DescribeValidDBInstanceModifications</a> to learn what modifications you can make to your DB
  instance. You can use this information when you call <a>ModifyDBInstance</a>.
  </p>
  
  @param describeValidDBInstanceModificationsRequest
  @return Result of the DescribeValidDBInstanceModifications operation returned by the service.
  @throws DBInstanceNotFoundException
  <i>DBInstanceIdentifier</i> does not refer to an existing DB instance.
  @throws InvalidDBInstanceStateException
  The specified DB instance is not in the <i>available</i> state.
  @sample AmazonNeptune.DescribeValidDBInstanceModifications
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/neptune-2014-10-31/DescribeValidDBInstanceModifications"
  target="_top">AWS API Documentation</a>