Trying to get data from firebase, but grouped 4 by 4. How would I manage to group and return an observable of 4 in 4.

```
# input
# [1, 2, 3, 4, 5, 6, 7, 8]

# output
# [ [1,2,3,4], [5, 6, 7, 8]...]

```

I have tried this, but it only takes the first 4 and returns an array and not as an observable

```js
this.data$ = this.afs
      .collection<Data>('data')
      .valueChanges()
      .pipe(take(4), toArray());

```