def _split_target(target):
    """
    split target to x, y, w, h, objectness, classification
    along dimension 2
    target is in shape [N, an_num, 6 + class_num, H, W]
    """
    tx = target[:, :, 0, :, :]
    ty = target[:, :, 1, :, :]
    tw = target[:, :, 2, :, :]
    th = target[:, :, 3, :, :]
    tscale = target[:, :, 4, :, :]
    tobj = target[:, :, 5, :, :]
    tcls = paddle.transpose(target[:, :, 6:, :, :], perm=[0, 1, 3, 4, 2])
    tcls.stop_gradient = True
    return (tx, ty, tw, th, tscale, tobj, tcls)

    split target to x, y, w, h, objectness, classification
    along dimension 2
    target is in shape [N, an_num, 6 + class_num, H, W]
    
ppdet/modeling/tests/test_yolov3_loss.py