In Course 4, W4, Lab1, during the model that runs 100 epoches to find the optimal learning rate, the infrastructure includes:

tf.keras.layers.Bidirectional(tf.keras.layers.LSTM(32, return_sequences=True)),

tf.keras.layers.Bidirectional(tf.keras.layers.LSTM(32, return_sequences=True)),

However, in the following model that trains for 500 epoches after picking the optimal running rate only has the regular LSTM layers:

tf.keras.layer

```
tf.keras.layers.LSTM(32, return_sequences=True),
tf.keras.layers.LSTM(32, return_sequences=True),
```

Is there a reason for this?