feat: add sum op for trainer controller (foundation-model-stack#491)

Signed-off-by: Mehant Kammakomati <mehant.kammakomati2@ibm.com>

Author: kmehant

tuning/utils/evaluator.py

@@ -117,6 +117,7 @@ def __init__(self, metrics: dict):
             "abs": abs,
             "len": len,
             "round": round,
+            "sum": sum,
             "math_trunc": math.trunc,
             "math_floor": math.floor,
             "math_ceil": math.ceil,