diff --git a/examples/bmn/bmn_metric.py b/examples/bmn/bmn_metric.py
index f9bf101f825913572803fbb1168260f83a0d96ac..d8e0d3e3ae307c9fa61000e336b4ef6864f956f2 100644
--- a/examples/bmn/bmn_metric.py
+++ b/examples/bmn/bmn_metric.py
@@ -39,11 +39,6 @@ class BmnMetric(Metric):
         elif self.mode == 'infer':
             self.get_infer_dataset_dict()
 
-    def add_metric_op(self, preds, label):
-        pred_bm, pred_start, pred_en = preds
-        video_index = label[-1]
-        return [pred_bm, pred_start, pred_en, video_index]  #return list
-
     def update(self, pred_bm, pred_start, pred_end, fid):
         # generate proposals
         pred_start = pred_start[0]
diff --git a/hapi/model.py b/hapi/model.py
index 05e8cec4c90ff401f68792b347843ef77643b85c..460916684c52b86ae1b76d8d0da801fd3b6e0cec 100644
--- a/hapi/model.py
+++ b/hapi/model.py
@@ -67,7 +67,7 @@ def to_list(value):
     if value is None:
         return value
     if isinstance(value, (list, tuple)):
-        return value
+        return list(value)
     return [value]