public function withdraw(string $asset, string $address, $amount, $addressTag = null)
    {
        $options = [
            "asset" => $asset,
            "address" => $address,
            "amount" => $amount,
            "wapi" => true,
            "name" => "API Withdraw",
        ];
        if (is_null($addressTag) === false && is_empty($addressTag) === false) {
            $options['addressTag'] = $addressTag;
        }
        return $this->httpRequest("v3/withdraw.html", "POST", $options, true);
    }