@Override
    public String getFunctionName(Method method, LambdaFunction annotation, LambdaInvokerFactoryConfig config) {
        String functionName = annotation.functionName();
        if (functionName.isEmpty()) {
            functionName = method.getName();
        }
        return functionName;
    }
Determine function name from the {@link LambdaFunction} annotation's functionName attribute if
present otherwise uses the method name.
aws-java-sdk-lambda/src/main/java/com/amazonaws/services/lambda/invoke/DefaultLambdaFunctionNameResolver.java