invoice = forms.ModelMultipleChoiceField(

        widget=forms.CheckboxSelectMultiple,

        queryset=commerce.Invoice.objects.all(),

    )

    from_email = forms.CharField()

    subject = forms.CharField()

    body = forms.CharField(

        widget=forms.Textarea,

    )

    action = forms.TypedChoiceField(

        widget=forms.RadioSelect,

        coerce=int,

        choices=ACTION_CHOICES,

        initial=ACTION_PREVIEW,

    )

    def __init__(self, *a, **k):

        category = k.pop('category', None) or []

        product = k.pop('product', None) or []

        category = [int(i) for i in category]

        product = [int(i) for i in product]

        qs = commerce.Invoice.objects.filter(

            status=commerce.Invoice.STATUS_UNPAID,

        ).filter(

            Q(lineitem__product__category__in=category) |

            Q(lineitem__product__in=product)

        )

        # Uniqify

        qs = commerce.Invoice.objects.filter(

            id__in=qs,

        )

        self.fields['invoice'].queryset = qs

        self.fields['invoice'].initial = [i.id for i in qs]