Django ManytoMany widget to CheckboxSelectMultiple and chained querysets

It happened that I needed a ManytoMany field to be displayed as a CheckboxSelectMultiple no problem with that. The trick part is that there are default fields to be displayed and a user should be able to add a new option and this option should be displayed on the form.

Here is what I did:

models.py

class Feature(models.Model):
   name = models.CharField( _("Feature Name"), max_length=40)
   default = models.BooleanField(_("Is Global Feature"), default = False)

class SomeModel(models.Model):
   features = models.ManyToManyField(Feature, related_name='features')

forms.py

class FeatureForm(forms.ModelForm):
def __init__(self, *args, **kwargs):
    somemodel = kwargs['somemodel']
    kwargs.pop('somemodel')
    super(SpaFeatureForm, self).__init__(*args, **kwargs)
    default_features = Feature.objects.filter(default=True)
   开发者_开发问答 custom_features = somemodel.features.filter(default=False)
    q_set = QuerySetChain(default_features, custom_features)
    self.fields['features'].widget = forms.CheckboxSelectMultiple()
    self.fields['features'].queryset = q_set

class Meta:
    model = m.Spa
    fields = ('features',)

I'll still implement the second part which will be a feature form and some sort of js to populate the Checkbox Multiselect field choices.

I modified @akaihola answer ow how to chain querysets changing def _all to def all. And it worked fine.

The question now is: Is that the best solution?