Restoring Trainable Variables from Saved Model

Start with the Java loading path shown in SavedModelBundle.load, model.function("serving_default"), and model.metaGraphDef(). Review how ConcreteFunction and SignatureDef expose a saved model, then determine whether trainable variable values are represented there. Done means documenting or enabling a Java-supported way to retrieve those values from the saved model.

I defined a model using Tensorflow 2 with a Model Sublassing API on Python

class BiLSTMModel(tf.keras.Model):

    def __init__(self, lstm_dims):
        super().__init__()
        self.ldims = lstm_dims
        self.blockLstm = FirstBlockLSTMModule(lstm_dims)
        self.nextBlockLstm = NextBlockLSTM(lstm_dims)

    def call(self, inputs):
        # Forward pass
        block_lstm1_output = self.blockLstm(inputs)
        block_lstm2_output = self.nextBlockLstm(block_lstm1_output)
        return block_lstm2_output

I implemented a custom training loop and after each epoch, I just save this Keras model

biLSTMModel = BiLSTMModel(lstm_dims)
for epoch in range(epochs):
 # Training code
 tf.saved_model.save(biLSTMModel, export_dir)

It generates the expected structure with assets and variables folders, along with saved_model.pb and variables files

Later on, when loading the model I can restore all trainable variables values of the model just like this:

loaded_bi_lstm = tf.saved_model.load(model_path)
infer_bi_lstm = loaded_bi_lstm.signatures["serving_default"]

# LSTM weights
w_first_lstm = tf.Variable(infer_bi_lstm.trainable_variables[0])
wig_first_lstm = tf.Variable(infer_bi_lstm.trainable_variables[1])
wfg_first_lstm = tf.Variable(infer_bi_lstm.trainable_variables[2])
wog_first_lstm = tf.Variable(infer_bi_lstm.trainable_variables[3])

The model on tensorflow-java is loading without errors.

@Test
public void shouldRestoreVariablesFromSavedModel() {
    SavedModelBundle model = SavedModelBundle.load(SAVED_MODEL_DP_PATH, SavedModelBundle.DEFAULT_TAG);
    ConcreteFunction concreteFunction = model.function("serving_default");

    //Trying to find some object that stores trainables variables data
    MetaGraphDef metaGraphDef = model.metaGraphDef();
    SignatureDef sig = metaGraphDef.getSignatureDefOrThrow("serving_default");
}

But I don't find a way to restore the trainable variables. When debugging, it seems there is no object that stores these data. Could you please guide me on how to get all trainable variables values from a saved model on Java.

Thanks