Evaluate on voc dataset.
    Args:
        pred_boxlists(list[BoxList]): pred boxlist, has labels and scores fields.
        gt_boxlists(list[BoxList]): ground truth boxlist, has labels field.
        iou_thresh: iou thresh
        use_07_metric: boolean
    Returns:
        dict represents the results

def eval_detection_voc(pred_boxlists, gt_boxlists, iou_thresh=0.5, use_07_metric=False):
    """Evaluate on voc dataset.
    Args:
        pred_boxlists(list[BoxList]): pred boxlist, has labels and scores fields.
        gt_boxlists(list[BoxList]): ground truth boxlist, has labels field.
        iou_thresh: iou thresh
        use_07_metric: boolean
    Returns:
        dict represents the results
    """
    assert len(gt_boxlists) == len(
        pred_boxlists
    ), "Length of gt and pred lists need to be same."
    prec, rec = calc_detection_voc_prec_rec(
        pred_boxlists=pred_boxlists, gt_boxlists=gt_boxlists, iou_thresh=iou_thresh
    )
    ap = calc_detection_voc_ap(prec, rec, use_07_metric=use_07_metric)
    return {"ap": ap, "map": np.nanmean(ap)}