code: public Discussion createDiscussion(long sheetId, Discussion discussion) throws SmartsheetException{
          Util.throwIfNull(sheetId, discussion);
          return this.createResource("sheets/" + sheetId + "/discussions",
                  Discussion.class, discussion);
      }
docs: Create a discussion on a sheet.
  
  It mirrors to the following Smartsheet REST API method: POST /sheets/{sheetId}/discussions
  
  @param sheetId the sheet id
  @param discussion the discussion object
  @return the created discussion
  @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