One way to get the persons missing PersonalNote objects.

biscuit/apps/alsijil/views.py

@@ -41,6 +41,15 @@ def lesson(request: HttpRequest, week: Optional[int] = None, period_id: Optional
             request.POST or None, instance=lesson_documentation, prefix='leson_documentation')
 
         # Create all missing personal notes about members of all groups in lesson
+
+        missing_pks = Person.objects.filter(
+            member_of__in=Group.objects.filter(pk__in=lesson_period.lesson.groups.all()),
+            is_active=True
+        ).exclude(
+            personal_notes__week=wanted_week,
+            personal_notes__lesson_period=lesson_period
+        ).values_list('pk', flat=True)
+
         for group in lesson_period.lesson.groups.all():
             for person in group.members.filter(is_active=True):
                 note, created = PersonalNote.objects.get_or_create(person=person, lesson_period=lesson_period,