title: Django admin - Mixing multiple model inlines in single admin interface
body: <p>I have a Django model layout that looks something like this:</p>
  
  <pre><code>class Author(models.Model):
      name = models.CharField(max_length=50, unique=True)
  
  class Publication(models.Model):
      author = models.ForeignKey(Author)        
  
      #Some shared fields
  
      class Meta:
          abstract = True
  
  class Book(Publication):
      #Book specific fields
  
  class Poem(Publication):
      #Poem specific fields
  </code></pre>
  
  <p>Generally speaking, I'd like to show information listed by author and sorted by some information, like pub_date, so that the end user would see something like:</p>
  
  <p>Author A: </p>
  
  <ul>
  <li>Poem 1</li>
  <li>Poem 2</li>
  <li>Book 1</li>
  <li>Poem 3</li>
  <li>Book 2</li>
  </ul>
  
  <p>Author B:</p>
  
  <ul>
  <li>Book 1</li>
  <li>Book 2</li>
  <li>Poem 1</li>
  <li>Poem 2</li>
  <li>Book 3</li>
  </ul>
  
  <p>And so on.  I can figure out how to display these on the front-end (I can either use django-polymorphic or simply combine the author.book_set.all() and author.poem_set.all() into a single list and sort).  But I CANNOT figure out how to implement this in the Admin site.  I would like the structure to be exactly the same as above -- so that when I click on Author A I'd get:</p>
  
  <ul>
  <li>inline for Poem 1</li>
  <li>inline for Poem 2</li>
  <li>inline for Book 1</li>
  <li>inline for Poem 3</li>
  <li>inline for Book 2</li>
  </ul>
  
  <p>If I simply attach Poem and Book as TabularInlines, they would be separated out into separate fieldsets, like so:</p>
  
  <ul>
  <li>inline for Poem 1</li>
  <li>inline for Poem 2</li>
  <li><p>inline for Poem 3</p></li>
  <li><p>inline for Book 1</p></li>
  <li>inline for Book 2</li>
  </ul>
  
  <p>But I think it's important for functionality that they are mixed together in a single fieldset (with the fields specific to the other child class either grayed out or not present for each inline).  Does anyone have any idea how to implement this?</p>