Braintree\CreditCardGateway::updateSignature PHP Method

    public static function updateSignature()
    {
        $options = self::baseOptions();
        $options[] = "failOnDuplicatePaymentMethod";
        $signature = self::baseSignature($options);
        $updateExistingBillingSignature = [['options' => ['updateExisting']]];
        foreach ($signature as $key => $value) {
            if (is_array($value) and array_key_exists('billingAddress', $value)) {
                $signature[$key]['billingAddress'] = array_merge_recursive($value['billingAddress'], $updateExistingBillingSignature);
            }
        }
        return $signature;
    }

 /**
  * create signatures for different call types
  * @ignore
  */
 public static function init()
 {
     self::$_createCustomerSignature = [self::$_transparentRedirectKeys, ['customer' => CustomerGateway::createSignature()]];
     self::$_updateCustomerSignature = [self::$_transparentRedirectKeys, 'customerId', ['customer' => CustomerGateway::updateSignature()]];
     self::$_transactionSignature = [self::$_transparentRedirectKeys, ['transaction' => TransactionGateway::createSignature()]];
     self::$_createCreditCardSignature = [self::$_transparentRedirectKeys, ['creditCard' => CreditCardGateway::createSignature()]];
     self::$_updateCreditCardSignature = [self::$_transparentRedirectKeys, 'paymentMethodToken', ['creditCard' => CreditCardGateway::updateSignature()]];
 }