Deepobserve does not observe changes in set

I'm trying to use deepObserve() with an object that has an ObservableSet field but the changes in this field are not reported.

class Foo {
  @observable barSet = new Set()
}

const foo = new Foo
deepObserve(foo, () => {
  console.log('foo changed')
})
foo.barSet.add('bar') // "foo changed" is not logged to the console

Is this something that is supported? I looked into the deepObserve code and found that it uses this function:

function isRecursivelyObservable(thing: any) {
    return isObservableObject(thing) || isObservableArray(thing) || isObservableMap(thing)
}

to determine whether an object can be observed but the isObservableSet check is missing.

Start by locating deepObserve and its isRecursivelyObservable helper, then inspect how observable objects, arrays, and maps are handled. Verify whether adding isObservableSet support makes changes to the ObservableSet trigger the callback, and add or update a regression test showing that foo.barSet.add('bar') is reported.