add filter on parent__isnull and childs__isnull=False
add filter on parent__isnull and childs__isnull=False

uclouvain/osis,uclouvain/osis,uclouvain/OSIS-Louvain,uclouvain/osis_louvain,uclouvain/OSIS-Louvain,uclouvain/osis,uclouvain/osis,uclouvain/osis_louvain,uclouvain/osis_louvain,uclouvain/OSIS-Louvain