Fix backwards compatibility with traitlets.

vidartf · Jun 11, 2023 · 24557c6 · 24557c6
1 parent a617943
commit 24557c6
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/ipydatawidgets/ndarray/union.py b/ipydatawidgets/ndarray/union.py
@@ -56,7 +56,8 @@ def set(self, obj, value):
             obj._notify_trait(self.name, old_value, new_value)
 
     def subclass_init(self, cls):
-        cls._instance_inits.append(self.instance_init)
+        if hasattr(cls, "_instance_inits"):
+            cls._instance_inits.append(self.instance_init)
         return super().subclass_init(cls)
 
     def instance_init(self, inst):