Class CheckboxGridValidation

// Add a checkbox grid item to a form and require one response per column.
var checkboxGridItem = form.addCheckboxGridItem();
checkboxGridItem.setTitle('Where did you celebrate New Years?')
  .setRows(['New York', 'San Francisco', 'London'])
  .setColumns(['2014', '2015', '2016', '2017']);
var checkboxGridValidation = FormApp.createCheckboxGridValidation()
  .setHelpText(“Select one item per column.”)
  .requireLimitOneResponsePerColumn()
  .build();
checkboxGridItem.setValidation(checkboxGridValidation);