title: How to access an object's fields and manipulate them when using pre_delete?
body: <p>I have a foreign key in the model and I want to change a field's value in that object when pre_delete is called. I'm new to this concept and just found out that you use a pre delete signal like this:</p>
  <pre class="lang-py prettyprint-override"><code>@receiver(pre_delete, sender=MyModel)
  def bid_deletion(sender, instance, using, **kwargs):
      pass
  </code></pre>
  <p>What should I write to use the foreign key object's field?</p>