<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def optimize(self, loss, num_async_replicas=1, use_tpu=False):
 """Return a training op minimizing loss."""

    lr = learning_rate.learning_rate_schedule(self.hparams)
    if num_async_replicas > 1:
      log_info("Dividing learning rate by num_async_replicas: %d",
               num_async_replicas)
    lr /= math.sqrt(float(num_async_replicas))
    train_op = optimize.optimize(loss, lr, self.hparams, use_tpu=use_tpu)
    return train_op