TypeError: issubclass() arg 1 must be a class

[Piecio]

When I run example application i get this error:

......\env\lib\site-packages\polymorphic\admin\parentadmin.py", line 91, in _lazy_setup
if self._child_models and not issubclass(self._child_models[0], models.Model):
TypeError: issubclass() arg 1 must be a class

[PeterBeklemishev]

Fix:
in admin.py replace

    child_models = (
        (models.CategoryNode, BaseChildAdmin),
        (models.TextNode, TextNodeAdmin),  # custom admin allows custom edit/delete view.
        (models.ImageNode, BaseChildAdmin),
    )

to

    child_models = (
        models.CategoryNode,
        models.TextNode,  # custom admin allows custom edit/delete view.
        models.ImageNode,
    )

and add

admin.site.register(models.CategoryNode, BaseChildAdmin)
admin.site.register(models.TextNode, TextNodeAdmin)
admin.site.register(models.ImageNode, BaseChildAdmin)

Explanation:
http://django-polymorphic.readthedocs.io/en/stable/admin.html

Changed in version 1.0: It’s now needed to register the child model classes too.

In django-polymorphic 0.9 and below, the child_models was a tuple of a (Model, ChildModelAdmin). The admin classes were registered in an internal class, and kept away from the main admin site. This caused various subtle problems with the ManyToManyField and related field wrappers, which are fixed by registering the child admin classes too. Note that they are hidden from the main view, unless show_in_index is set.