I'm new to Django and MPTT and having hard time figuring out how to get all leaf nodes and send them directly to Form class.
For example, I have created MPTT Category Model, and have hierarchy like this:

* Category1
+ Category2
+ Category3

* Category4
+ Category5
+ Category6

So I want only to get leaf categories(cat2,3,5,6).My Form class looks something like this:

```
class UploadForm(forms.Form):
    description = forms.CharField(max_length=50)
    category = mpttform.TreeNodeMultipleChoiceField(queryset=Category.objects.all())
    file = forms.FileField() 

```

And with queryset=Category.objects.all() I get exactly the same thing above - all Categories and its children.Is there a way I can get only leaf nodes(children), but leaf nodes from ALL categories, not from specific Category instance ? Thanks.