code: @Override
      public DescribeActivityResult describeActivity(DescribeActivityRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeActivity(request);
      }
docs: <p>
  Describes an activity.
  </p>
  <note>
  <p>
  This operation is eventually consistent. The results are best effort and may not reflect very recent updates and
  changes.
  </p>
  </note>
  
  @param describeActivityRequest
  @return Result of the DescribeActivity operation returned by the service.
  @throws ActivityDoesNotExistException
  The specified activity does not exist.
  @throws InvalidArnException
  The provided Amazon Resource Name (ARN) is invalid.
  @sample AWSStepFunctions.DescribeActivity
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/states-2016-11-23/DescribeActivity" target="_top">AWS API
  Documentation</a>