Unable to import models in __init__.py django 1.9.4

My directory structure is.

Mypack:
  --> __init__.py
  --> admin.py
  --> apps.py
  --> foo.py
  --> models.py

In apps.py, I have AppConfig. I have some methods in foo.py which uses the models imported from models.py. and I imported all methods in init.py.

from foo import *

I make this app installable with pip. when I install it in other django app and try to run python manage.py check. it gives the following error.

django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.

please suggest me, how to fix this issue?