code: public function getNeighbours($namespace, $callback, $id)
      {
          $list = $this->getList($namespace, $callback);
          $list->setCurrent($id);
          return [
              $list->getPrevious(),
              $list->getNext()
          ];
      }
docs: Get previous and next id from the list.
  
  @param string $namespace
  @param RepositoryInterface|callable $callback
  @param string $id Current application id
  @return array
  first entry: previous id or null
  second entry: next id or null