Update ref-metrics.py

ref-metrics.py

@@ -102,7 +102,7 @@ class UserFriendlyMetrics(evaluate.Metric):
         return self.dummy_values()
         # return calculate(predictions, references, max_iou)
 
-    def dummy_values():
+    def dummy_values(self):
         return {
             "model_1": {
                 "overall": {