code: @Override
      public DescribeDBEngineVersionsResult describeDBEngineVersions(DescribeDBEngineVersionsRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeDBEngineVersions(request);
      }
docs: <p>
  Returns a list of the available DB engines.
  </p>
  
  @param describeDBEngineVersionsRequest
  @return Result of the DescribeDBEngineVersions operation returned by the service.
  @sample AmazonNeptune.DescribeDBEngineVersions
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/neptune-2014-10-31/DescribeDBEngineVersions"
  target="_top">AWS API Documentation</a>