fix NameError and AttribteError
diff --git a/planetstack/observer/steps/sync_slice_memberships.py b/planetstack/observer/steps/sync_slice_memberships.py
index 0e9d681..2748fcd 100644
--- a/planetstack/observer/steps/sync_slice_memberships.py
+++ b/planetstack/observer/steps/sync_slice_memberships.py
@@ -1,5 +1,6 @@
 import os
 import base64
+from django.db.models import F, Q
 from planetstack.config import Config
 from observer.openstacksyncstep import OpenStackSyncStep
 from core.models.slice import *