[NFC] polish _checkpoint_hook.py code style (#1722)

colossalai/trainer/hooks/_checkpoint_hook.py

@@ -50,32 +50,23 @@ class SaveCheckpointHook(BaseHook):
                 break
         self.model = self.model if self.model is not None else trainer.engine.model
 
-    
     def after_train_iter(self, trainer, output, label, loss):
         """Saves the model after a training iter.
         """
         # save by interval
         if self.save_by_iter and trainer.cur_step % self.interval == 0:
-            save_checkpoint(self.checkpoint_dir,
-                            trainer.cur_epoch,
-                            self.model,
-                            trainer.engine.optimizer,
+            save_checkpoint(self.checkpoint_dir, trainer.cur_epoch, self.model, trainer.engine.optimizer,
                             self._lr_scheduler)
-            self.logger.info(
-                f'checkpoint for iteration {trainer.cur_step} is saved to {self.checkpoint_dir}', ranks=[0])
+            self.logger.info(f'checkpoint for iteration {trainer.cur_step} is saved to {self.checkpoint_dir}',
+                             ranks=[0])
         else:
             pass
 
-
     def after_train_epoch(self, trainer):
         """Saves the model after a training epoch.
         """
         # save by interval
         if trainer.cur_epoch % self.interval == 0:
-            save_checkpoint(self.checkpoint_dir,
-                            trainer.cur_epoch,
-                            self.model,
-                            trainer.engine.optimizer,
+            save_checkpoint(self.checkpoint_dir, trainer.cur_epoch, self.model, trainer.engine.optimizer,
                             self._lr_scheduler)
-            self.logger.info(
-                f'checkpoint for epoch {trainer.cur_epoch} is saved to {self.checkpoint_dir}', ranks=[0])
+            self.logger.info(f'checkpoint for epoch {trainer.cur_epoch} is saved to {self.checkpoint_dir}', ranks=[0])