how to pass user id values to parameters in django?

I have a code where I need to pass the user_from id (the user from whom the message comes), but when I write user_from__pk writes an error that there is no such name

NameError: name ‘user_from__pk’ is not defined

My code:

views.py:

def send_chat(request):
    resp = {}
    User = get_user_model()
    if request.method == 'POST':
        post =request.POST
        u_from = UserModel.objects.get(id=post['user_from'])
        u_to = UserModel.objects.get(id=post['user_to'])
        messages = request.user.received.all()
        pk_list = messages.values(user_from__pk).distinct()
        correspondents = get_user_model().objects.filter(pk__in=list(pk_list))
        insert = chatMessages(user_from=u_from,user_to=u_to,message=post['message'], correspondents=correspondents)
        try:
            insert.save()
            resp['status'] = 'success'
        except Exception as ex:
            resp['status'] = 'failed'
            resp['mesg'] = ex
    else:
        resp['status'] = 'failed'

    return HttpResponse(json.dumps(resp), content_type="application/json")

models.py:

class chatMessages(models.Model):
    user_from = models.ForeignKey(User,
        on_delete=models.CASCADE,related_name="sent")
    user_to = models.ForeignKey(User,
        on_delete=models.CASCADE,related_name="received")
    message = models.TextField()
    date_created = models.DateTimeField(default=timezone.now)
    correspondents = models.ForeignKey(User,
        on_delete=models.CASCADE,related_name="correspondents", null=True)

    def __str__(self):
        return self.message

how can I pass the user_from id in the line:

pk_list = messages.values(user_from__pk).distinct()

>Solution :

.values() method accepts field names as string. So, it should be .values("user_from__pk")