title: Making inlines conditional in the Django admin
body: <p>I have a model that I want staff to be able to edit up to the date for the event. Like this:</p>
  
  <pre><code>class ThingAdmin(admin.ModelAdmin):
      model = Thing
  
      if obj.date &lt; today: #Something like that
          inlines = [MyInline,]
  </code></pre>
  
  <p>The problem is, I don't have access to the obj instance at this level. I've tried overriding get_formset(), but didn't get anywhere.</p>
  
  <p>Please advise?</p>