Added django.contrib.sites.managers, which contains CurrentSiteManager. Thanks, Ian Holsman

from django.db import models

from django.conf import settings

class CurrentSiteManager(models.Manager):

    "Use this to limit objects to those associated with the current site."

    def __init__(self, field_name='site')

        super(SiteLimitManager, self).__init__()

        self.__lookup = field_name + '__id__exact'

    def get_query_set(self):

        return super(SiteLimitManager, self).get_query_set().filter(self.__lookup=settings.SITE_ID)