Performs non-maximum suppression on a boxlist, with scores specified
    in a boxlist field via score_field.

    Arguments:
        boxlist(BoxList)
        nms_thresh (float)
        max_proposals (int): if > 0, then only the top max_proposals are kept
            after non-maximum suppression
        score_field (str)

def boxlist_nms(boxlist, nms_thresh, max_proposals=-1, score_field="scores"):
    """
    Performs non-maximum suppression on a boxlist, with scores specified
    in a boxlist field via score_field.

    Arguments:
        boxlist(BoxList)
        nms_thresh (float)
        max_proposals (int): if > 0, then only the top max_proposals are kept
            after non-maximum suppression
        score_field (str)
    """
    if nms_thresh <= 0:
        return boxlist
    mode = boxlist.mode
    boxlist = boxlist.convert("xyxy")
    boxes = boxlist.bbox
    score = boxlist.get_field(score_field)
    keep = _box_nms(boxes, score, nms_thresh)
    if max_proposals > 0:
        keep = keep[: max_proposals]
    boxlist = boxlist[keep]
    return boxlist.convert(mode)