如何使用Keras连接两个LSTM？

from keras.models import Model
from keras.layers import Input, LSTM, concatenate

input_shape1 = ...
input_shape2 = ...

# 定义LSTM1模型
input1 = Input(shape=(input_shape1, ))
lstm1 = LSTM(units=...)(input1)
model1 = Model(inputs=input1, outputs=lstm1)

# 定义LSTM2模型
input2 = Input(shape=(input_shape2, ))
lstm2 = LSTM(units=...)(input2)
model2 = Model(inputs=input2, outputs=lstm2)

# 连接两个LSTM模型
concatenated = concatenate([model1.output, model2.output])

# 定义连接后的模型
output = ...
model = Model(inputs=[model1.input, model2.input], outputs=output)