private function initRelations() {
    if ($this->relations == null) {
      $this->relations = [];
      $this->relations['byrole'] = [];
      $this->relations['bytype'] = [];

      $relations = $this->getRelations();
      foreach ($relations as $relation) {
        $this->relations['byrole'][$relation->getOtherRole()] = $relation;
        $otherType = $relation->getOtherType();
        if (!isset($this->relations['bytype'][$otherType])) {
          $this->relations['bytype'][$otherType] = [];
        }
        $this->relations['bytype'][$otherType][] = $relation;
        $this->relations['bytype'][$this->persistenceFacade->getSimpleType($otherType)][] = $relation;
      }
    }
  }