code: def on_train_begin(self, pbar, **kwargs:Any)->None:
          "Initialize optimizer and learner hyperparameters."
          setattr(pbar, 'clean_on_interrupt', True)
          self.learn.save('tmp')
          self.opt = self.learn.opt
          self.opt.lr = self.sched.start
          self.stop,self.best_loss = False,0.
          return {'skip_validate': Truef on_train_begin(self, pbar, **kwargs:Any)->None:
          "Initialize optimizer and learner hyperparameters."
          setattr(pbar, 'clean_on_interrupt', True)
          self.learn.save('tmp')
          self.opt = self.learn.opt
          self.opt.lr = self.sched.start
          self.stop,self.best_loss = False,0.
          return {'skip_validate': True}
docs: Initialize optimizer and learner hyperparameters.