def mse_loss_backward(y_true, y_pred):
    """均方误差反向

    :param y_true: shape[N, Out]
    :param y_pred: shape[N, Out]
    :return: shape[N, Out]"""

    N = y_true.shape[0]  # batch_size
    return 2 * (y_pred - y_true) / N