public function sendFusionTransaction(
        int $threshold,
        int $anonymity,
        array $addresses = null,
        string $destinationAddress = null
    ):JsonResponse {
        $params = [
            'threshold' => $threshold,
            'anonymity' => $anonymity,
        ];

        if (!is_null($addresses)) $params['addresses'] = $addresses;
        if (!is_null($destinationAddress)) $params['destinationAddress'] = $destinationAddress;

        return $this->rpcPost('sendFusionTransaction', $params);
    }