Braintree\PaymentMethodGateway::baseSignature PHP Method

    private static function baseSignature()
    {
        $billingAddressSignature = AddressGateway::createSignature();
        $optionsSignature = ['failOnDuplicatePaymentMethod', 'makeDefault', 'verificationMerchantAccountId', 'verifyCard', 'verificationAmount'];
        return ['billingAddressId', 'cardholderName', 'cvv', 'deviceData', 'expirationDate', 'expirationMonth', 'expirationYear', 'number', 'paymentMethodNonce', 'token', ['options' => $optionsSignature], ['billingAddress' => $billingAddressSignature]];
    }