Deleting an unsaved fragment from store

Hello,
I'm very sure I'm doing this incorrectly. I have a route for creating a model setup as shown:

```
export default Route.extend(AuthenticatedRouteMixin, {
model() {
return RSVP.hash({
systemDatasource: this.store.createRecord('system-datasource', {
name: null,
basePath: null,
datasourceType: null,
s3: this.store.createFragment('system-datasource-s3', {
'bucket': null,
'basePath': null,
'accessKey': null,
'secretKey': null
}),
sftp: this.store.createFragment('system-datasource-sftp', {})
}),
datasourceList: ['s3','sftp']
})
},

actions: {
discard() {
let systemDatasource = this.modelFor(this.routeName).systemDatasource;
systemDatasource.deleteRecord();
this.transitionTo('settings.system-datasources');
}
}
});
```

When I call the `discard()` method (i.e. user decides to abort creating a new object), I notice the uncommitted `system-datasource` model is removed from the store correctly.

However, the `system-datasource-s3` and `system-datasource-sftp` models are left behind:


Can you kindly advise on how I can go about removing those unsaved fragments from the store? Thank you so much!