void run_optimization(OptimizerV2 optimizer, Tensor x, Tensor y)
{
using var g = tf.GradientTape();
var pred = conv_net(x);
var loss = cross_entropy(pred, y);
// Compute gradients.
var trainable_variables = new IVariableV1[] { wc1, wc2, wd1, wout, bc1, bc2, bd1, bout };
var gradients = g.gradient(loss, trainable_variables);
// Update W and b following gradients.
optimizer.apply_gradients(zip(gradients, trainable_variables.Select(x => x as ResourceVariable)));
}