feat: change checkpoint save path

'saved_models/checkpoint.pt' --> 'checkpoint.pt'

pytorchtools.py

@@ -33,5 +33,5 @@ def __call__(self, val_loss, model):
     def save_checkpoint(self, val_loss, model):
         '''Saves model when validation loss decrease.'''
         print(f'Validation loss decreased ({self.val_loss_min:.6f} --> {val_loss:.6f}).  Saving model ...')
-        torch.save(model.state_dict(), 'saved_models/checkpoint.pt')
+        torch.save(model.state_dict(), 'checkpoint.pt')
         self.val_loss_min = val_loss