Are the auto-* selectors supposed to match every item?

Hey there,

thanks a lot for this and your other great emacs-packages. I really enjoy `org-super-agenda`, however, I have a hard time wrapping my head around the auto-type selectors. In particular, I'd like to restrict them to items matched by some other selector. E.g., I have the following in my config:

```
(setq org-super-agenda-groups
'((:name "Project Actions"
:auto-parent t
:and (:children nil
:todo t
:tag "PROJECT"))
(:discard (:anything t))))
```
What I want to achieve here, is to grouping all items matching the `:and` expression by their parent and discard all other items. However, all items seem to end up in the first group. I also tried the following
```
(setq org-super-agenda-groups
'((:name "Project Actions"
:auto-parent (:and (:children nil
:todo t
:tag "PROJECT")))
(:discard (:anything t))))
```

to the same effect. My third try looked liked this
```
(setq org-super-agenda-groups
'((:name "Project Actions"
:and (:auto-parent t
:children nil
:todo t
:tag "PROJECT"))
(:discard (:anything t))))
```
and led to an error as soon as I opened the agenda. Is there a way to combine the `:auto-parent`-selector with the normal selectors?

Thanks again for your work and happy holidays :-)