code: @Override
      public EvaluateExpressionResult evaluateExpression(EvaluateExpressionRequest request) {
          request = beforeClientExecution(request);
          return executeEvaluateExpression(request);
      }
docs: <p>
  Task runners call <code>EvaluateExpression</code> to evaluate a string in the context of the specified object.
  For example, a task runner can evaluate SQL queries stored in Amazon S3.
  </p>
  
  @param evaluateExpressionRequest
  Contains the parameters for EvaluateExpression.
  @return Result of the EvaluateExpression operation returned by the service.
  @throws InternalServiceErrorException
  An internal service error occurred.
  @throws TaskNotFoundException
  The specified task was not found.
  @throws InvalidRequestException
  The request was not valid. Verify that your request was properly formatted, that the signature was
  generated with the correct credentials, and that you haven't exceeded any of the service limits for your
  account.
  @throws PipelineNotFoundException
  The specified pipeline was not found. Verify that you used the correct user and account identifiers.
  @throws PipelineDeletedException
  The specified pipeline has been deleted.
  @sample DataPipeline.EvaluateExpression
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/datapipeline-2012-10-29/EvaluateExpression"
  target="_top">AWS API Documentation</a>