from keras.layers import Input, Dense
from keras.models import Model
import keras

input_inner = Input(shape=(4,), name='input_inner')
output_inner = Dense(3, name='inner_dense')(input_inner)
inner_model = Model(inputs=input_inner, outputs=output_inner)

input = Input(shape=(5,), name='input')
output = inner_model(input)

model = Model(inputs=input, outputs=output)