review_object = Review.objects.filter(property_id=prop.values('id')).annotate(total=Sum('star_rating'))

count_stars = 0
    for ro in review_object:
        count_stars += ro.star_rating

review_object = Review.objects.values('property_id').annotate(total=Sum('star_rating'))

from collections import defaultdict

review_object = Review.objects.all()
results = defaultdict(int)
for ro in review_object:
    results[ro.property_id] += ro.star_rating