Update examples/mnist_lightning.py

Co-authored-by: Karthik Prasad <prasadkr@uci.edu>

Author: dwahdany

examples/mnist_lightning.py

@@ -100,7 +100,7 @@ def configure_optimizers(self):
 
         if self.enable_dp:
             self.trainer.fit_loop.setup_data()
-            dataloader = self.trainer.train_dataloader
+            data_loader = self.trainer.train_dataloader
 
             # transform (model, optimizer, dataloader) to DP-versions
             if hasattr(self, "dp"):