Add description of input param

[dsantiago]

Just for completness, could add the description of valid_anchors_wh and num_classes (although num_classes is intuitive)

https://github.com/ethanyanjiali/deep-vision/blob/6765dfcc36f209d2fded00fb11c6d1ae0da8e658/YOLO/tensorflow/yolov3.py#L245

[ethanyanjiali]

thanks for the advice. i'll add it when i have time. valid_anchors_wh is the width, height tuple for anchors.