code: def save_form(self, commit=True):
          
          return super(SuperModelFormMixin, self).save(commit=commit)
docs: This calls Django's ``ModelForm.save()``. It only takes care of
          saving this actual form, and leaves the nested forms and formsets
          alone.
  
          We separate this out of the
          :meth:`~django_superform.forms.SuperModelForm.save` method to make
          extensibility easier.