No export of callable response in django_tablib.admin.TablibAdmin

[Uznick]

When I use callables in list_display as is explained in https://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.list_display, django-tablib just ignores this field.

I think, that's wrong behaviour and it should also export the result of the callable with other model fields.