site_filter = Filter(Site.fields, site_filter)
sql += " AND (%s) %s" % site_filter.sql(api, "AND")
elif isinstance (site_filter, StringTypes):
site_filter = Filter(Site.fields, site_filter)
sql += " AND (%s) %s" % site_filter.sql(api, "AND")
elif isinstance (site_filter, StringTypes):