yolov3-tf2-master ，tensorflow版本，dataset.py文件有transform_targets函数，代码如下：
def transform_targets(y_train, anchors, anchor_masks, size):
y_outs = []
grid_size = size // 32
# calculate anchor index for true boxes
anchors = tf.cast(anchors, tf.float32)
anchor_area = anchors[..., 0] * anchors[..., 1]
box_wh = y_train[..., 2:4] - y_train[..., 0:2]
box_wh = tf.tile(tf.expand_dims(box_wh, -2),
(1, 1, tf.shape(anchors)[0], 1))
box_area = box_wh[..., 0] * box_wh[..., 1]
intersection = tf.minimum(box_wh[..., 0], anchors[..., 0]) * \
tf.minimum(box_wh[..., 1], anchors[..., 1]) 是计算交集，请问是怎样计算方法？这两行代码没看明白