code: public Comment addCommentWithAttachment(long sheetId, long discussionId, Comment comment, File file, String contentType) throws SmartsheetException, IOException{
          String path = "sheets/" + sheetId + "/discussions/" + discussionId + "/comments";
          Util.throwIfNull(sheetId, comment, file, contentType);
  
          return this.addCommentWithAttachment(path, comment, new FileInputStream(file), contentType, file.getName());
      }
docs: Add a comment to a discussion with an attachment.
  
  It mirrors to the following Smartsheet REST API method: POST /discussion/{discussionId}/comments
  
  @param sheetId the sheet id
  @param discussionId the dicussion id
  @param comment the comment to add
  @param file the file to be attached
  @param contentType the type of file
  @return the created comment
  @throws IllegalArgumentException if any argument is null or empty string
  @throws InvalidRequestException if there is any problem with the REST API request
  @throws AuthorizationException if there is any problem with  the REST API authorization (access token)
  @throws ResourceNotFoundException if the resource cannot be found
  @throws ServiceUnavailableException if the REST API service is not available (possibly due to rate limiting)
  @throws SmartsheetException if there is any other error during the operation
  @throws IOException is there is any error with file