code: @Override
      public AddAttachmentsToSetResult addAttachmentsToSet(AddAttachmentsToSetRequest request) {
          request = beforeClientExecution(request);
          return executeAddAttachmentsToSet(request);
      }
docs: <p>
  Adds one or more attachments to an attachment set. If an <code>attachmentSetId</code> is not specified, a new
  attachment set is created, and the ID of the set is returned in the response. If an <code>attachmentSetId</code>
  is specified, the attachments are added to the specified set, if it exists.
  </p>
  <p>
  An attachment set is a temporary container for attachments that are to be added to a case or case communication.
  The set is available for one hour after it is created; the <code>expiryTime</code> returned in the response
  indicates when the set expires. The maximum number of attachments in a set is 3, and the maximum size of any
  attachment in the set is 5 MB.
  </p>
  
  @param addAttachmentsToSetRequest
  @return Result of the AddAttachmentsToSet operation returned by the service.
  @throws InternalServerErrorException
  An internal server error occurred.
  @throws AttachmentSetIdNotFoundException
  An attachment set with the specified ID could not be found.
  @throws AttachmentSetExpiredException
  The expiration time of the attachment set has passed. The set expires 1 hour after it is created.
  @throws AttachmentSetSizeLimitExceededException
  A limit for the size of an attachment set has been exceeded. The limits are 3 attachments and 5 MB per
  attachment.
  @throws AttachmentLimitExceededException
  The limit for the number of attachment sets created in a short period of time has been exceeded.
  @sample AWSSupport.AddAttachmentsToSet
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/support-2013-04-15/AddAttachmentsToSet" target="_top">AWS
  API Documentation</a>