refactor: Extract get_stream_subscriptions_for_user().

zerver/lib/stream_subscription.py

@@ -4,6 +4,7 @@ from django.db.models.query import QuerySet
 from zerver.models import (
     Recipient,
     Subscription,
+    UserProfile,
 )
 
 def get_active_subscriptions_for_stream_id(stream_id):
@@ -22,6 +23,13 @@ def get_active_subscriptions_for_stream_ids(stream_ids):
         active=True
     )
 
+def get_stream_subscriptions_for_user(user_profile):
+    # type: (UserProfile) -> QuerySet
+    return Subscription.objects.filter(
+        user_profile=user_profile,
+        recipient__type=Recipient.STREAM,
+    )
+
 def num_subscribers_for_stream_id(stream_id):
     # type: (int) -> int
     return get_active_subscriptions_for_stream_id(stream_id).filter(