public function isEmpty($propertyName)
{
if (!$this->classSchema->isMultiValuedProperty($propertyName)) {
throw new InvalidQueryException('Property "' . $propertyName . '" must be multi-valued', 1276853547);
}
return $this->qomFactory->comparison($this->qomFactory->propertyValue($propertyName, '_entity'), QueryInterface::OPERATOR_IS_EMPTY);
}