如何在Django rest框架中获得具有父模型前景键的子模型？

from django.db import models

class ParentModel(models.Model):
    name = models.CharField(max_length=100)

class ChildModel(models.Model):
    parent = models.ForeignKey(ParentModel, on_delete=models.CASCADE)
    child_name = models.CharField(max_length=100)

from rest_framework import serializers

class ChildSerializer(serializers.ModelSerializer):
    class Meta:
        model = ChildModel
        fields = ('id', 'child_name')

class ParentSerializer(serializers.ModelSerializer):
    children = ChildSerializer(many=True, read_only=True)

    class Meta:
        model = ParentModel
        fields = ('id', 'name', 'children')

from rest_framework import viewsets

class ParentViewSet(viewsets.ModelViewSet):
    queryset = ParentModel.objects.all()
    serializer_class = ParentSerializer

from django.urls import path, include
from rest_framework import routers

router = routers.DefaultRouter()
router.register('parents', ParentViewSet)

urlpatterns = [
    path('', include(router.urls)),
]