protected function scopedKey($node)
{
$attributes = $this->scopedAttributes($node);
$output = [];
foreach ($attributes as $fld => $value) {
$output[] = $this->qualify($fld) . '=' . (is_null($value) ? 'NULL' : $value);
}
// NOTE: Maybe an md5 or something would be better. Should be unique though.
return implode(',', $output);
}