title: Update an Object/Instance by overwriting the save method of another Model, by using the FK
body: <p>I have the following models:</p>
  
  <pre><code> class Acc(models.Model):
          name = models.CharField( max_length=35)
  
  class User(AbstractBaseUser, PermissionsMixin):
  
      acc = models.ForeignKey(Acc, blank=True, null=True, related_name='owner', on_delete=models.CASCADE)
  
  
  class Note(models.Model):
      name = models.CharField( max_length=35
      receiver = models.ForeignKey(settings.AUTH_USER_MODEL, blank=True, null=True, on_delete=models.CASCADE)
  
  class Item(models.Model):
      note = models.ForeignKey(Notification, on_delete=models.CASCADE,)
      acc = models.ForeignKey(Acc, on_delete=models.CASCADE)
  
      def save(self, *args, **kwargs):
  
          .....
          # update note
          Note.objects.filter(id=self.note_id).update(receiver=self.account.owner)
  </code></pre>
  
  <p>I overwrite the <code>save</code> method on the <code>Item</code> Object/Model, to update the <code>Note</code> Model <code>receiver</code> using the ForeignKey.</p>
  
  <p>I get the following error:</p>
  
  <pre><code>int() argument must be a string, a bytes-like object or a number, not 'RelatedManager'
  </code></pre>
  
  <p>it is triggered by this line:</p>
  
  <pre><code>Note.objects.filter(id=self.note_id).update(receiver=self.acc.owner)
  </code></pre>
  
  <p>The <code>owner</code> is the related manager of the <code>Acc</code> Model and is a <code>User</code>Model, which I want to get for <code>receiver</code> key in Note.</p>