code: @Override
      public StartDocumentClassificationJobResult startDocumentClassificationJob(StartDocumentClassificationJobRequest request) {
          request = beforeClientExecution(request);
          return executeStartDocumentClassificationJob(request);
      }
docs: <p>
  Starts an asynchronous document classification job. Use the operation to track the progress of the job.
  </p>
  
  @param startDocumentClassificationJobRequest
  @return Result of the StartDocumentClassificationJob operation returned by the service.
  @throws InvalidRequestException
  The request is invalid.
  @throws TooManyRequestsException
  The number of requests exceeds the limit. Resubmit your request later.
  @throws ResourceNotFoundException
  The specified resource ARN was not found. Check the ARN and try your request again.
  @throws ResourceUnavailableException
  The specified resource is not available. Check to see if the resource is in the <code>TRAINED</code>
  state and try your request again.
  @throws KmsKeyValidationException
  The KMS customer managed key (CMK) entered cannot be validated. Verify the key and re-enter it.
  @throws InternalServerException
  An internal server error occurred. Retry your request.
  @sample AmazonComprehend.StartDocumentClassificationJob
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/comprehend-2017-11-27/StartDocumentClassificationJob"
  target="_top">AWS API Documentation</a>