diff --git a/api/change_set.py b/api/change_set.py
index fbcd489..6d9b4df 100644
--- a/api/change_set.py
+++ b/api/change_set.py
@@ -14,9 +14,9 @@ class ChangeSet:
         self.operations.append({ 'operation': 'update', 'type': type, 'id': id, 'properties': properties })
         return self
 
-    def append(self, other) -> None:
+    def append(self, other):
         self.operations += other.operations
         return self
 
-    def compress(self) -> None:
+    def compress(self):
         return self