How to produce a two-level group by in Obsidian using dataview

Question

I store notes in Obsidian which have various properties, the frontmatter looks like this:

---
level_1: <l1 property value>
level_2: <l2 property value>
title: <note title>
---

I'd like to produce a dataview table consisting of a two-level grouping, such that my data looks like the following (i.e. note Bar has level_1 = A, level_2 = B, and note Boz has level_1 = D):

Level 1  Level 2  Title
-------  -------  -----
A        B        Foo
                  Bar
D        E        Faz
         F        Boz

I have seen a (small-ish) number of references online purporting to solve this, but cannot get any of them to give me what I want.

This is the sort of thing I've been trying, but it doesn't group by l1 or l2 correctly (only one l1 is shown and all l2s are show whether or not they ought to be hidden):

```dataview
TABLE without id 
    level_1 as "Level 1", 
    rows.rows.level_2 as "Level 2",
    rows.rows.date,
    link(rows.rows.Title, Title) as Title
GROUP BY "Level 2"
GROUP BY rows.level_1[0]
```

Can I write a dataview query to give me what I want?