class NumberForm(forms.ModelForm):

    def __init__(self, *args, **kwargs):
        self.room_queryset = kwargs.pop('room_queryset', None)
        super(NumberForm, self).__init__(*args, **kwargs)
        self.fields['rooms'].queryset = self.room_queryset

    rooms = forms.ModelChoiceField(label='Room', queryset = Room.objects.none())

    class Meta:
        model = Number
        fields = ('country','routing_rule','rooms')