def bbox_xyxy2xywh(bbox_xyxy: np.ndarray) -> np.ndarray:
    """Transform the bbox format from x1y1x2y2 to xywh.

    Args:
        bbox_xyxy (np.ndarray): Bounding boxes (with scores), shaped (n, 4) or
            (n, 5). (left, top, right, bottom, [score])

    Returns:
        np.ndarray: Bounding boxes (with scores),
          shaped (n, 4) or (n, 5). (left, top, width, height, [score])
    """
    bbox_xywh = bbox_xyxy.copy()
    bbox_xywh[:, 2] = bbox_xywh[:, 2] - bbox_xywh[:, 0]
    bbox_xywh[:, 3] = bbox_xywh[:, 3] - bbox_xywh[:, 1]

    return bbox_xywh
Transform the bbox format from x1y1x2y2 to xywh.

    Args:
        bbox_xyxy (np.ndarray): Bounding boxes (with scores), shaped (n, 4) or
            (n, 5). (left, top, right, bottom, [score])

    Returns:
        np.ndarray: Bounding boxes (with scores),
          shaped (n, 4) or (n, 5). (left, top, width, height, [score])
    
mmpose/mmpose/structures/bbox/transforms.py