public function toDTO($filterByKey = null)
    {
        if (! $this->getAttribute("recipient") || ! $this->getAttribute("mosaicId"))
            return [];

        return [
            "type" => $this->type,
            "recipient" => $this->recipient()->address()->toClean(),
            "mosaicId" => $this->mosaicId()->toDTO(),
            "fee" => $this->fee,
        ];
    }