def box_iou(boxes1: Tensor, boxes2: Tensor) -> Tensor:
    """
    Return intersection-over-union (Jaccard index) between two sets of boxes.

    Both sets of boxes are expected to be in ``(x1, y1, x2, y2)`` format with
    ``0 <= x1 < x2`` and ``0 <= y1 < y2``.

    Args:
        boxes1 (Tensor[N, 4]): first set of boxes
        boxes2 (Tensor[M, 4]): second set of boxes

    Returns:
        Tensor[N, M]: the NxM matrix containing the pairwise IoU values for every element in boxes1 and boxes2
    """
    inter, union = _box_inter_union(boxes1, boxes2)
    iou = inter / union
    return iou

    Return intersection-over-union (Jaccard index) between two sets of boxes.

    Both sets of boxes are expected to be in ``(x1, y1, x2, y2)`` format with
    ``0 <= x1 < x2`` and ``0 <= y1 < y2``.

    Args:
        boxes1 (Tensor[N, 4]): first set of boxes
        boxes2 (Tensor[M, 4]): second set of boxes

    Returns:
        Tensor[N, M]: the NxM matrix containing the pairwise IoU values for every element in boxes1 and boxes2
    
test/external/mlperf_retinanet/model/boxes.py