Add an extra description

youden_index.py

@@ -25,6 +25,7 @@ _DESCRIPTION = """
 This metric computes the Youden index based on the area under the curve (AUC) for the Receiver Operating Characteristic Curve (ROC). 
 The return values represent the ideal point in the ROC curve, where max(TPR - FPR) holds true (across all points in the curve).
 This metric only works with binary labels: The case in which there are only two different label classes, and each example gets only one label.
+The prediction_scores are the probabilities for the positive class.
 """
 
 _KWARGS_DESCRIPTION = """