Draw top3 proposals for each gt.
    Args:
        proposals: NPx4
        proposal_scores: NP
        gt_boxes: NG

def draw_proposal_recall(img, proposals, proposal_scores, gt_boxes):
    """
    Draw top3 proposals for each gt.
    Args:
        proposals: NPx4
        proposal_scores: NP
        gt_boxes: NG
    """
    box_ious = np_iou(gt_boxes, proposals)    # ng x np
    box_ious_argsort = np.argsort(-box_ious, axis=1)
    good_proposals_ind = box_ious_argsort[:, :3]   # for each gt, find 3 best proposals
    good_proposals_ind = np.unique(good_proposals_ind.ravel())

    proposals = proposals[good_proposals_ind, :]
    tags = list(map(str, proposal_scores[good_proposals_ind]))
    img = viz.draw_boxes(img, proposals, tags)
    return img, good_proposals_ind