error code about content_object in Django Genericforeignkey

error message

FieldError at /member/brand/productmanage/checkarrived/9
Field 'content_object' does not generate an automatic reverse relation and therefore cannot be used for reverse querying. If it is a GenericForeignKey, consider adding a GenericRelation.
Request Method:	GET
Request URL:	http://localhost:8000/member/brand/productmanage/checkarrived/9?ptype=productitem
Django Version:	2.0.6
Exception Type:	FieldError
Exception Value:	
Field 'content_object' does not generate an automatic reverse relation and therefore cannot be used for reverse querying. If it is a GenericForeignKey, consider adding a GenericRelation.
Exception Location:	/home/ubuntu/ohua/testenv/lib/python3.5/site-packages/django/db/models/sql/query.py in names_to_path, line 1360
Python Executable:	/home/ubuntu/ohua/testenv/bin/python

Traceback

/home/ubuntu/ohua/gitrepo/pypro/member/views.py in checkarrived
            TL.first = ProductPackageClass.objects.filter(package=tl).order_by('date','time').first()
            TL.date = TL.first.start_date
            TL.time = TL.first.start_time
    else :
        raise Http404
    
    product = TL.product
    orderitems = OrderItem.objects.filter(product=product,content_object=TL) ...
    context = {
        'TL': TL,
        'orderitems': orderitems,
    }
    return render(request, 'checkarrived.html', context)

▼ Local vars
Variable	Value
TL	
<ProductItem: 課程a　的課程時間>
id	
9
product	
<Product: 課程[email protected]>
request	
<WSGIRequest: GET '/member/brand/productmanage/checkarrived/9?ptype=productitem'>

views.py

@login_required
def checkarrived(request, id):
    # if this product is not yours , you should get 404                                                                                      
    # TL = Time & Location , whatever productitem or productpackage                                                                          
    if request.GET.get('ptype', False) :
        if request.GET.get('ptype') == 'productitem' :
            TL = ProductItem.objects.get(id=id)
            TL.date = TL.start_date
            TL.time = TL.start_time
        else :
            TL = ProductPackage.objects.get(id=id)
            TL.first = ProductPackageClass.objects.filter(package=tl).order_by('date','time').first()
            TL.date = TL.first.start_date
	    TL.time = TL.first.start_time
    else :
        raise Http404

    product = TL.product
    orderitems = OrderItem.objects.filter(product=product,content_object=TL)
    context = {
        'TL': TL,
        'orderitems': orderitems,
    }
    return render(request, 'checkarrived.html', context)