django how to access info in query set code example

Example 1: pass in queryset as filter django

users = UserClasses.objects.filter(class_id=data['class_id'])
user_details = User.objects.filter(id__in=users.values_list('id', flat=True))

Example 2: get queryset

class PurchaseList(generics.ListAPIView):
    serializer_class = PurchaseSerializer

    def get_queryset(self):
        """
        Optionally restricts the returned purchases to a given user,
        by filtering against a `username` query parameter in the URL.
        """
        queryset = Purchase.objects.all()
        username = self.request.query_params.get('username', None)
        if username is not None:
            queryset = queryset.filter(purchaser__username=username)
        return queryset