--- a/doc/tutorials/advanced/part04_ui-base.rst	Wed Feb 27 13:41:34 2019 +0100
+++ b/doc/tutorials/advanced/part04_ui-base.rst	Tue Feb 26 16:23:07 2019 +0100
@@ -176,6 +176,7 @@
 
     from cubes.folder import entities as folder
 
+
     class FolderITreeAdapter(folder.FolderITreeAdapter):
 
         def different_type_children(self, entities=True):