Adding PolymorphicChildModelAdmin to __all__ as well

polymorphic/admin.py

@@ -17,7 +17,7 @@ from django.utils.safestring import mark_safe
 from django.utils.translation import ugettext_lazy as _
 import abc
 
-__all__ = ('PolymorphicModelChoiceForm', 'PolymorphicParentModelAdmin')
+__all__ = ('PolymorphicModelChoiceForm', 'PolymorphicParentModelAdmin', 'PolymorphicChildModelAdmin')
 
 
 class PolymorphicModelChoiceForm(forms.Form):