code: @Override
      public DescribeDBInstancesResult describeDBInstances(DescribeDBInstancesRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeDBInstances(request);
      }
docs: <p>
  Returns information about provisioned instances. This API supports pagination.
  </p>
  
  @param describeDBInstancesRequest
  @return Result of the DescribeDBInstances operation returned by the service.
  @throws DBInstanceNotFoundException
  <i>DBInstanceIdentifier</i> does not refer to an existing DB instance.
  @sample AmazonNeptune.DescribeDBInstances
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/neptune-2014-10-31/DescribeDBInstances" target="_top">AWS
  API Documentation</a>