The IDL union type can be used for a parameter that will need to pass one of a small number of types. Use it to define the type of a parameter that is sometimes empty and sometimes has the type Value.

What will be an ideal response?

```
union ValueOption switch (boolean){
case TRUE: Value value;
};
```
When the value of the tag is TRUE, a Value is passed. When it is FALSE, only the tag is passed.