Echo JS 0.11.0

I have a class `Data` which holds data and not functions as its value. Can I implement a `contramap` method that obeys the contravariant functor laws for that class?

```
class Data {
  constructor(value) {
    this.value = value;
  }

  map(f) {
    return new Data(f(this.value));
  }

  contramap(f) {
    // ???
  }
}
```