appElement, {
            sheets: [
              {
                id: 'employees',
                label: 'Employees',
                columns: [
                  {
                    label: 'Employee ID',
                    id: 'employee_id',
                    type: 'number',
                    validators: [
                      { validate: 'required' },
                      {
                        validate: 'unique',
                        error: 'This employee ID is not unique',
            