pep8: Fix E301 pep8 violations.

Fix "E301: expected (1 or 2) blank line" pep8 violations.

zerver/models.py

@@ -852,6 +852,7 @@ def bulk_get_recipients(type, type_ids):
     def cache_key_function(type_id):
         # type: (int) -> Text
         return get_recipient_cache_key(type, type_id)
+
     def query_function(type_ids):
         # type: (List[int]) -> Sequence[Recipient]
         # TODO: Change return type to QuerySet[Recipient]