Guided Backpropagation at inference time with Tensorflow 2

guided_backprop.py

with tf.GradientTape() as tape:
    conv_outputs, predictions = grad_model(np.array([img]))
    loss = predictions[:, CAT_CLASS_INDEX]

output = conv_outputs[0]
grads = tape.gradient(loss, conv_outputs)[0]

# Apply guided backpropagation
gate_f = tf.cast(output > 0, 'float32')
gate_r = tf.cast(grads > 0, 'float32')
guided_grads = tf.cast(output > 0, 'float32') * tf.cast(grads > 0, 'float32') * grads

Hi, is this conv_outputs means the last layers?
if so, how to hook the first layer for gradient