public function trunks()
{
$grammar = $this->getConnection()->getQueryGrammar();
$rgtCol = $grammar->wrap($this->getQualifiedRightColumnName());
$lftCol = $grammar->wrap($this->getQualifiedLeftColumnName());
return $this->descendants()->whereNotNull($this->getQualifiedParentColumnName())->whereRaw($rgtCol . ' - ' . $lftCol . ' != 1');
}