code: public List<Column> addColumns(long sheetId, List<Column> columns) throws SmartsheetException {
          return this.postAndReceiveList("sheets/" + sheetId + "/columns", columns, Column.class);
      }
docs: Add column to a sheet.
  
  It mirrors to the following Smartsheet REST API method: POST /sheets/{sheetId}/columns
  
  Exceptions:
  IllegalArgumentException : if any argument is null
  InvalidRequestException : if there is any problem with the REST API request
  AuthorizationException : if there is any problem with the REST API authorization(access token)
  ResourceNotFoundException : if the resource can not be found
  ServiceUnavailableException : if the REST API service is not available (possibly due to rate limiting)
  SmartsheetRestException : if there is any other REST API related error occurred during the operation
  SmartsheetException : if there is any other error occurred during the operation
  
  @param sheetId the sheet id
  @param columns the list of columns object limited to the following attributes: *
  title * type * symbol (optional) * options (optional) - array of options * index (zero-based) * systemColumnType
  (optional) * autoNumberFormat (optional)
  @return the list of created columns
  @throws SmartsheetException the smartsheet exception