code: def clip_boxes(boxes, window, name=None):
      
      boxes = tf.maximum(boxes, 0.0)
      m = tf.tile(tf.reverse(window, [0]), [2])    # (4,)
      boxes = tf.minimum(boxes, tf.cast(m, tf.float32), name=name)
      return boxes
docs: Args:
          boxes: nx4, xyxy
          window: [h, w]