silverstripe-framework/tests/security/PermissionCheckboxSetFieldTest.yml

'SilverStripe\Security\Group':
  group:
    Code: group
  untouchable:
    Code: untouchable
'SilverStripe\Security\Permission':
  perm1:
    Code: ADMIN
    Group: '=>SilverStripe\Security\Group.untouchable'
  perm2:
    Code: NON-ADMIN