[pl_examples] revert deletion of optimizer_step (#5227)

examples/lightning_base.py

@@ -116,6 +116,19 @@ class BaseTransformer(pl.LightningModule):
         self.opt = optimizer
         return [optimizer]
 
+    def optimizer_step(self, epoch, batch_idx, optimizer, optimizer_idx, second_order_closure=None):
+        if self.trainer.use_tpu:
+            xm.optimizer_step(optimizer)
+        else:
+            optimizer.step()
+        optimizer.zero_grad()
+        self.lr_scheduler.step()
+
+    def get_tqdm_dict(self):
+        avg_loss = getattr(self.trainer, "avg_loss", 0.0)
+        tqdm_dict = {"loss": "{:.3f}".format(avg_loss), "lr": self.lr_scheduler.get_last_lr()[-1]}
+        return tqdm_dict
+
     def test_step(self, batch, batch_nb):
         return self.validation_step(batch, batch_nb)