src/Baum/Move.php
protected function parentId() {
    switch( $this->position ) {
      case 'root':
        return NULL;

      case 'child':
        return $this->target->getKey();

      default:
        return $this->target->getParentId();
    }
  }
protected function parentId() {
    switch( $this->position ) {
      case 'root':
        return NULL;

      case 'child':
        return $this->target->getKey();

      default:
        return $this->target->getParentId();
    }
  }
Computes the new parent id for the node being moved.

@return int