public function jsonSerialize() {
        return [
            'id' => $this->id,
            'comboSetId' => $this->comboSetId,
            'label' => $this->label,
            'optional' => $this->optional,
            'enableMultiSelect' => $this->enableMultiSelect,
            'position' => $this->position,
            'items' => $this->items,
            'createdAt' => $this->createdAt,
            'updatedAt' => $this->updatedAt,
        ];
    }