@Override
    public StringBuilder toString(StringBuilder string, SerializationContext context, Deque<String> path, CompositeNode parent) {
        return generator.toString(string, context, path, this);
    }
Returns this as an operator which converts a list of integers into a double.
searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/GeneratorLambdaFunctionNode.java