DJANGO: ModelChoiceField optgroup tag

An extension of @Stefan Manastirliu answer to use with django-categories. (Downside is that get_tree_data() function below allows only one level) . In combination with javascript plugins like bootstrap multiselect you can get multi-select like

Models.py

from categories.models import CategoryBase
class SampleCategory(CategoryBase):
    class Meta:
        verbose_name_plural = 'sample categories'

class SampleProfile(models.Model):
    categories = models.ManyToManyField('myapp.SampleCategory')

forms.py

from myapp.models import SampleCategory

    def get_tree_data():
        def rectree(toplevel):
            children_list_of_tuples = list()
            if toplevel.children.active():
                for child in toplevel.children.active():
                    children_list_of_tuples.append(tuple((child.id,child.name)))

            return children_list_of_tuples

        data = list()
        t = SampleCategory.objects.filter(active=True).filter(level=0)
        for toplevel in t:
            childrens = rectree(toplevel)
            data.append(
                tuple(
                    (
                        toplevel.name,
                        tuple(
                            childrens
                            )
                        ) 
                    )
            )
        return tuple(data)

class SampleProfileForm(forms.ModelForm):
    categories = forms.MultipleChoiceField(choices=get_tree_data())
    class Meta:
        model = SampleProfile

Here's a good snippet:

Choice Field and Select Widget With Optional Optgroups: http://djangosnippets.org/snippets/200/

You don't need to create any custom field, Django already does the job, just pass the choices well formatted:

MEDIA_CHOICES = (
 ('Audio', (
   ('vinyl', 'Vinyl'),
   ('cd', 'CD'),
  )
 ),
 ('Video', (
   ('vhs', 'VHS Tape'),
   ('dvd', 'DVD'),
  )
 ),
)