public static LambdaConfigurationStaxUnmarshaller getInstance() {
        return instance;
    }
CloudFunctionConfiguration is a little different then Topic or Queue Configurations and thus
doesn't fit nicely as a subclass of {@link NotificationConfigurationStaxUnmarshaller}. A
CloudFunctionConfiguration element may be unmarshalled into two different classes based on
presence of the InvocationRole attribute. If InvocationRole is present we unmarshall into the
legacy {@link CloudFunctionConfiguration}, otherwise we unmarshall into
{@link LambdaConfiguration}.
aws-java-sdk-s3/src/main/java/com/amazonaws/services/s3/model/transform/LambdaConfigurationStaxUnmarshaller.java