Python 3.x ValueError:endog需要有ndim 1，但有ndim 2

我正在尝试应用指数平滑。。我的密码是

from statsmodels.tsa.holtwinters import ExponentialSmoothing
model = ExponentialSmoothing(data3, trend="add", seasonal="add", seasonal_periods=12)
model2 = ExponentialSmoothing(data3, trend="add", seasonal="add", seasonal_periods=12, damped=True)
fit1=model.fit()
pred1=fit1.forcast(24)
fit2=model2.fit()
pred2=fit2.forcast(24)
sse1 = np.sqrt(np.mean(np.square(test_x.values-pred1.values)))
sse2 = np.sqrt(np.mean(np.square(test_x.values-pred2.values)))

它显示了这个错误

ValueError: endog is required to have ndim 1 but has ndim 2 

有人能帮忙吗？ 先谢谢你