fixup! fix: show correct icons in the sidebar for units with custom XBlocks

Author: Agrendalath

lms/djangoapps/course_home_api/outline/serializers.py

@@ -82,7 +82,11 @@ def get_vertical_icon_class(block):
             video
         """
         children = block.get('children', [])
-        child_classes = {value for child in children for value in (child.get('type'), child.get('icon_class'))}
+        child_classes = {
+            value
+            for child in children
+            for value in (child.get('type'), child.get('icon_class'))
+        }
         if 'problem' in child_classes:
             return 'problem'
         if 'video' in child_classes: