I am trying to save a trained model but its giving me this kind of error "NameError: name 'tfjs' is not defined" Can someone help me out?

This is the code I have written:

#Saves the structure of the model
model_json=model.to_json()
tfjs.converters.save_keras_model(model, './exported-model')
with open(model-new.json, w) as json_file:
    json_file.write(model_json)