Django: inlineformset‘属性没有与其关联的文件’错误

# models.py
from django.db import models

class ParentModel(models.Model):
    # 主表模型
    name = models.CharField(max_length=100)

class ChildModel(models.Model):
    # 子表模型
    parent = models.ForeignKey(ParentModel, on_delete=models.CASCADE)
    file = models.FileField(upload_to='files/')

# forms.py
from django.forms import inlineformset_factory

ChildFormSet = inlineformset_factory(ParentModel, ChildModel, fields=('file',), extra=1)

# views.py
from django.shortcuts import render
from .forms import ChildFormSet

def my_view(request):
    parent = ParentModel.objects.get(id=1)
    formset = ChildFormSet(instance=parent, data=request.POST or None, files=request.FILES or None)
    if request.method == 'POST':
        if formset.is_valid():
            formset.save()
            # 处理保存成功后的逻辑
    else:
        formset = ChildFormSet(instance=parent)
    return render(request, 'my_template.html', {'formset': formset})

# my_template.html
<form method="post" enctype="multipart/form-data">
    {{ formset.management_form }}
    {% for form in formset %}
        {{ form }}
    {% endfor %}
    <input type="submit" value="Save">
</form>