存在ManyToMany关系的FilterSet

Question

基本型号：

class ModelA(Model):
    name = CharField(...)


class ModelB(Model):
    model_a = ManyToManyField(ModelA, blank=True)

class ModelBFilter(filters.FilterSet):
    unassigned = BooleanFilter(field_name='model_a', lookup_expr='isnull')

    class Meta:
        model = ModelB
        fields = ['unassigned']

如何过滤（用django-filter ）来查找没有相应相关模型的ModelB？