public function save() {
    $state = ['end' => $this->end, 'oidList' => $this->oidList, 'processedOidList' => $this->processedOidList,
      'currentOID' => $this->currentOid, 'currentDepth' => $this->currentDepth, 'aggregationKinds' => $this->aggregationKinds];
    $this->session->set($this->id, $state);
  }