The `.create()` method does not support writable nested fields by default

I am new to Django REST, I was trying to make some entry to the DB using the serilaizer in django rest. But i am getting some errors while using the create method.

My models are,

class CoreInformation(models.Model):
        site_name = models.CharField(max_length=145, blank=True, null=True)
        status = models.CharField(max_length=45, blank=True, null=True)
        created_at = models.DateTimeField(blank=True, null=True, auto_now_add=True)

        class Meta:
            managed = False
            db_table = 'core_information'

class CoreDetailInformation(models.Model):
    core_info = models.ForeignKey('CoreInformation', models.DO_NOTHING, related_name='core_base_info')
    old_sac = models.CharField(max_length=45, blank=True, null=True)
    msc = models.CharField(max_length=45, blank=True, null=True)

    class Meta:
        db_table = 'core_detail_information'

And i have two ModelSerializer like below ,

class CoreDetailSerializer(serializers.ModelSerializer):

    class Meta:
        model = CoreDetailInformation
        fields = ('id','old_sac', 'msc')


class CustomCoreInfoSerializer(serializers.ModelSerializer):
    core_base_info = CoreDetailSerializer(many=True)

    class Meta:
        model = CoreInformation
        # fields = '__all__'
        fields = ('id', 'site_name', 'status', 'created_at', 'core_base_info')

        @transaction.atomic
        def create(self, validated_data):
            try:
                with transaction.atomic():
                    base_info = CoreInformation.objects.create(site_name=validated_data['site_name'],status=validated_data['status']                                         
                    for site_detail in validated_data['core_base_info']:
                        CoreDetailInformation.objects.get_or_create(msc=site_detail['msc'],old_sac=site_detail['old_sac'],core_info=base_info)
            except CoreInformation.DoesNotExist as e:
                raise e
            except CoreDetailInformation.DoesNotExist as e:
                raise e

and my views.py is ,

class CoreInformation(generics.ListCreateAPIView):
    queryset = models.CoreInformation.objects.all()
    serializer_class = CustomCoreInfoSerializer

    def create(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        instance = self.perform_create(serializer)
        serializer = self.get_serializer(instance=instance)
        return Response(serializer.data, status=status.HTTP_201_CREATED)

    def perform_create(self, serializer):
        return serializer.create(validated_data=serializer.validated_data)

To create the CoreInformation my input will be like below,

{
    "site_name": "xxxxxxxxxx",
    "status": "create",
    "core_base_info": [{
                "old_sac": '1',
                "msc": "abc1,abc2"
            },
            {
                "old_sac": '2',
                "msc": "abc3,abc4"
            }]
}

But when i am compiling its returns me the below error,

AssertionError at /api/core/
The `.create()` method does not support writable nested fields by default.
Write an explicit `.create()` method for serializer `src.core.serializers.CustomCoreInfoSerializer`, or set `read_only=True` on nested serializer fields.

I found this , but did n't help for me.

Any help would be greatly appreciated. Thanks.