Returns the filtered queryset based on the value
        provided in the query string and retrievable via
        `self.value()`.

def queryset(self, request, queryset):
        """
        Returns the filtered queryset based on the value
        provided in the query string and retrievable via
        `self.value()`.
        """
        if self.value():
            parent = Question.objects.get(slug=self.value())
            return Choice.objects.child_of(parent).order_by('-id')
        return queryset