25
In order to count the number of occurrences of each type, you have to group by the type field. In Django this is done by using values to get just that field. So, this should work:
Item.objects.values('group').annotate(
type_count=models.Count("type")
).filter(type_count__gt=1).order_by("-type_count")
3
It’s logical error 
type_count__gt=1 means type_count > 1 so if the count == 1 it won’t be displayed 
use type_count__gte=1 instead – it means type_count >= 1
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Source:stackexchange.com