如何使用inline_formsety在模型/表单上的clean()函数中排除已删除的对象

from django.forms import inlineformset_factory
from django.core.exceptions import ValidationError

class ParentModel(models.Model):
    # 父模型字段

class ChildModel(models.Model):
    parent = models.ForeignKey(ParentModel, on_delete=models.CASCADE)
    # 子模型字段

class ChildForm(forms.ModelForm):
    class Meta:
        model = ChildModel
        fields = '__all__'

ChildFormSet = inlineformset_factory(ParentModel, ChildModel, form=ChildForm, extra=1)

class ParentForm(forms.ModelForm):
    class Meta:
        model = ParentModel
        fields = '__all__'

    def clean(self):
        cleaned_data = super().clean()
        child_formset = ChildFormSet(self.instance, self.data, self.files)

        if not child_formset.is_valid():
            raise ValidationError('子表单数据无效')

        # 排除已删除的子对象
        if self.instance.pk:
            deleted_child_ids = set(self.instance.childmodel_set.values_list('id', flat=True)) - set(child_formset.cleaned_data)
            ChildModel.objects.filter(id__in=deleted_child_ids).delete()

        return cleaned_data