code: protected function filterNestedEmptyGroups(AclPresenceInterface $presence)
      {
          if ($presence['type'] !== AclPresenceType::GROUP) {
              return 1;
          }
  
          $permissions = $presence->permissions();
  
          if ( ! $permissions) {
              return 0;
          }
  
          if (is_string($permissions)) {
              return 1;
          }
  
          return count($permissions);
      }
docs: Removes any empty group children from a tree structure, returning
  the number of non-group entries.
  
  @param AclPresenceInterface $presence
  @return int  the number of non-group children found on the levels below