src/transformers/trainer.py/Trainer/create_optimizer_and_scheduler
class Trainer:    def create_optimizer_and_scheduler(self, num_training_steps: int):
        """
        Setup the optimizer and the learning rate scheduler.

        We provide a reasonable default that works well. If you want to use something else, you can pass a tuple in the
        Trainer's init through :obj:`optimizers`, or subclass and override this method (or :obj:`create_optimizer`
        and/or :obj:`create_scheduler`) in a subclass.
        """
        self.create_optimizer()
        self.create_scheduler(num_training_steps=num_training_steps, optimizer=self.optimizer)