Django serialization

Question

serialization is not getting all values

i have this object and and assign a property to it, but in a moment of serialization the value that i assign is not serialized

@login_required(login_url='auth:login') def get_instance_provisioning(request):

instance_pk = request.GET.get('instance_pk')
viewpoints_list = CViewPoint.objects.filter(instance_id=instance_pk)
five_mins = timedelta(minutes=5)
ten_mins = timedelta(minutes=10)
now_time = timezone.now()

paginator = Paginator(viewpoints_list, 1)
viewpoints = []

page = request.GET.get('page')

try:
    viewpoints = paginator.page(page)
except PageNotAnInteger:
    # If page is not an integer, deliver first page.
    viewpoints = paginator.page(1)
except EmptyPage:
    # If page is out of range (e.g. 9999), deliver last page of results.
    viewpoints = paginator.page(paginator.num_pages)



for viewpoint in viewpoints:
    # checkedIn info
    checked_in = PmsCheckin.objects.filter(
        cviewpoint=viewpoint).order_by('id')
    viewpoint.is_checkedin = "checked-in-status" if len(
        checked_in) > 0 else "checked-out-status"

 data = serialize("json", viewpoints) 
 return JsonResponse(data)