private function loadValidatorAttribute(array &$property, AttributeItem $attribute)
    {
        /* @var $element Element */
        $type = $attribute->getType();

        $this->loadValidatorType($property, $type, false);

        // Required properties
        if ($attribute instanceof Attribute) {
            if ($attribute->getUse() === Attribute::USE_REQUIRED) {
                $property['validation'][] = [
                    'NotNull' => null
                ];
            }
        }
    }