OSIS-2202 use lambda instead of external function
OSIS-2202 use lambda instead of external function

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