Django - Annotate field - django

Question

I have 3 models:
1.
class Calendar(models.Model):
...
supplier = models.CharField(...)
subassort = models.CharField(..., null=True)
Data example:
supplier | subassort
----------------------
12345 | subassort1
67890 | subassort2
class SupplierProductAssortments(models.Model):
subassort = models.CharField(...)
supplier = models.CharField(...)
ui2_code = models.CharField(...)
Data example:
supplier | subassort | ui2_code
---------------------------------
12345 | subassort1 | ui-1
12345 | subassort1 | ui-2
67890 | subassort2 | ui-3
class UI2(models.Model):
code = models.CharField(...)
name = models.CharField(...)
Data example:
code | name
-------------
ui-1 | milk
ui-2 | cheese
ui-3 | meat
I need to annotate ui2 field to queryset of Calendar. For better understanding below I wrote a function that demonstrates it:
def get_calendars_with_ui2s():
calendars = Calendar.objects.all() # need to annotate ui2 names
for calendar in calendars:
if subassort := calendar.subassort:
ui2_codes = SupplierProductAssortments.objects\
.filter(supplier=calendar.supplier, subassort=subassort)\
.values_list('ui2_code', flat=True)
ui2 = UI2.objects.filter(code__in=ui2_codes).values_list('name', flat=True)
else:
ui2 = []
calendar.ui2 = ui2
return calendars
Expected output:
supplier | subassort | ui2
---------------------------------------
12345 | subassort1 | [milk, cheese]
67890 | subassort2 | [meat]
If when filtering ui2_codes was by one field I guess it could be solved by OuterRef. But there are filtering by two fields.
How can I annotate field ui2?
P.S. No FK