code: @Override
      public DescribeAssociationResult describeAssociation(DescribeAssociationRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeAssociation(request);
      }
docs: <p>
  Describes the association for the specified target or instance. If you created the association by using the
  <code>Targets</code> parameter, then you must retrieve the association by using the association ID. If you
  created the association by specifying an instance ID and a Systems Manager document, then you retrieve the
  association by specifying the document name and the instance ID.
  </p>
  
  @param describeAssociationRequest
  @return Result of the DescribeAssociation operation returned by the service.
  @throws AssociationDoesNotExistException
  The specified association does not exist.
  @throws InvalidAssociationVersionException
  The version you specified is not valid. Use ListAssociationVersions to view all versions of an
  association according to the association ID. Or, use the <code>$LATEST</code> parameter to view the
  latest version of the association.
  @throws InternalServerErrorException
  An error occurred on the server side.
  @throws InvalidDocumentException
  The specified document does not exist.
  @throws InvalidInstanceIdException
  The following problems can cause this exception:</p>
  <p>
  You do not have permission to access the instance.
  </p>
  <p>
  SSM Agent is not running. On managed instances and Linux instances, verify that the SSM Agent is running.
  On EC2 Windows instances, verify that the EC2Config service is running.
  </p>
  <p>
  SSM Agent or EC2Config service is not registered to the SSM endpoint. Try reinstalling SSM Agent or
  EC2Config service.
  </p>
  <p>
  The instance is not in valid state. Valid states are: Running, Pending, Stopped, Stopping. Invalid states
  are: Shutting-down and Terminated.
  @sample AWSSimpleSystemsManagement.DescribeAssociation
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/ssm-2014-11-06/DescribeAssociation" target="_top">AWS API
  Documentation</a>