private static TResult ExecuteResultOperator <TSource, TResult>(
            IEnumerable <TSource> source, ResultOperatorBase resultOperator, StreamedSequenceInfo streamedSequenceInfo)
        {
            var streamedData
                = resultOperator.ExecuteInMemory(
                      new StreamedSequence(source, streamedSequenceInfo));

            return((TResult)streamedData.Value);
        }