Dodesn't seem to make any difference: guess it does work with the object reference

synapse/storage/end_to_end_keys.py

@@ -52,7 +52,6 @@ class EndToEndKeyStore(SQLBaseStore):
                 )
                 for row in rows:
                     user_result[row["device_id"]] = row["key_json"]
-                result[user_id] = user_result
             return result
         return self.runInteraction("get_e2e_device_keys", _get_e2e_device_keys)