yolo.py header (#3347)

models/yolo.py

@@ -1,4 +1,8 @@
-# YOLOv5 YOLO-specific modules
+"""YOLOv5-specific modules
+
+Usage:
+    $ python path/to/models/yolo.py --cfg yolov5s.yaml
+"""
 
 import argparse
 import logging