title: Django admin, Use ImportExportModelAdmin and MarkdownxModelAdmin (Multiple)
body: <p>I have model Product.
  1) There is markdownx field (from django-markdownx package) and I want use markdown editor in admin
  2) I use import-export in admin for this model.</p>
  
  <p>I can make *import-export** works by using <strong>ImportExportModelAdmin</strong>:</p>
  
  <pre><code>from import_export.admin import ImportExportModelAdmin
  class ProductAdmin(ImportExportModelAdmin): [some_code...]
  admin.site.register(Product, ProductAdmin)
  </code></pre>
  
  <p>I can make <strong>markdownx</strong> works by using <strong>MarkdownxModelAdmin</strong>: </p>
  
  <pre><code>from markdownx.admin import MarkdownxModelAdmin
  class ProductAdmin(MarkdownxModelAdmin): [some_code...]
  admin.site.register(Product, ProductAdmin)
  </code></pre>
  
  <p>How to make them both works? </p>