title: Django import export add on existing admin
body: <p>I am trying to use django import-export UI admin part. I can make it work in vanilla stage but when I want to implement it to admin I already have I get problems.</p>
  
  <p>If we go with this example here 
  <a href="https://django-import-export.readthedocs.io/en/latest/getting_started.html#admin-integration" rel="nofollow noreferrer">https://django-import-export.readthedocs.io/en/latest/getting_started.html#admin-integration</a></p>
  
  <p>I am adding </p>
  
  <pre><code>class BookAdmin(ImportExportModelAdmin):
      resource_class = BookResource
  </code></pre>
  
  <p>and then I need to register that like</p>
  
  <pre><code>admin.site.register(Book, BookAdmin) 
  </code></pre>
  
  <p>so it shows up, problem is that I already have this line above as I have a BookAdmin where I change how regular admin looks like</p>
  
  <pre><code>class BookAdmin(admin.ModelAdmin):
  </code></pre>
  
  <p>So I need to try to add import/export class with some different name like 
  class BookAdminExport, but then I cant register it to admin anymore as if I try
   admin.site.register(Book, BookAdminExport) it says "The model book is already registered" so I dont have any ideas what to do next?</p>