NameError：未定义名称“模型”

Question

我使用keras做了一个简单的分类器，并试图将其保存并转换为tf文件，最终可以在android studio中使用它，但是在以下代码后出现错误：

    from keras.models import model_from_json
from keras.models import load_model

# serialize model to JSON
#  the keras model which is trained is defined as 'model' in this example
model_json = model.to_json()


with open("model_num.json", "w") as json_file:
    json_file.write(model_json)

# serialize weights to HDF5
model.save_weights("model_num.h5")

错误是NameError：名称'model'未定义

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