Class which takes multiple django querysets and returns an optionally sorted, merged version

gistfile1.txt

Usage is:
OrderedMixedQuerysets('-date',MyModel.objects.all(),MyOtherModel.objects.all())

orderdmixedqueryset.py

#Inspired by http://stackoverflow.com/questions/431628/how-to-combine-2-or-more-querysets-in-a-django-view
class OrderedMixedQuerysets:
    reverse = False

    def __init__(self, order_by, *querysets):
        self.querysets = querysets
        self.order_by = order_by
        if self.order_by and self.order_by.startswith('-'):
            self.reverse = True
            self.order_by = self.order_by[1:]

    def count(self):
        """
        Performs a .count() for all subquerysets and returns the number of
        records as an integer.
        """
        return sum(qs.count() for qs in self.querysets)

    def _clone(self):
        "Returns a clone of this queryset chain"
        return self.__class__(*self.querysets, order_by=self.order_by)

    def all(self):
        "Iterates records in all subquerysets"
        if self.order_by:
            object_list = sorted(chain(*self.querysets), key=attrgetter(self.order_by))
            if self.reverse:
                object_list = reversed(object_list)
        else:
            object_list = chain(*self.querysets)
        return object_list

    def __getitem__(self, ndx):
        if type(ndx) is slice:
            return list(islice(self.all(), ndx.start, ndx.stop, ndx.step or 1))
        else:
            return islice(self.all(), ndx, ndx+1).next()