code: private function doDeleteAdministratorRole(int $administratorId, int $roleId): ?int
      {
          $q = new QueryBuilder("DELETE FROM ".self::ADM_ROLES_TABLE_NAME." WHERE administrator_id = $1 AND role_id = $2", $administratorId, $roleId);
          try {
              $deletedId = $q->executeWithReturnField('id');
          } catch (Exceptions\QueryResultsNotFoundException $e) {
              return null;
          }
          return (int) $deletedId;
      }
docs: returns null if not found