Add non-context manager tutorial for PyTorch Tensorboard plugin (#1723)

* Add non-context manager tutorial for PyTorch Tensorboard plugin

* add split line in tutorials

* fix bugs

Author: guotuofeng

intermediate_source/tensorboard_profiler_tutorial.py

@@ -132,6 +132,20 @@ def train(data):
         train(batch_data)
         prof.step()  # Need to call this at the end of each step to notify profiler of steps' boundary.
 
+######################################################################
+# Alternatively, the following non-context manager start/stop is supported as well.
+prof = torch.profiler.profile(
+        schedule=torch.profiler.schedule(wait=1, warmup=1, active=3, repeat=2),
+        on_trace_ready=torch.profiler.tensorboard_trace_handler('./log/resnet18'),
+        record_shapes=True,
+        with_stack=True)
+prof.start()
+for step, batch_data in enumerate(train_loader):
+    if step >= (1 + 1 + 3) * 2:
+        break
+    train(batch_data)
+    prof.step()
+prof.stop()
 
 ######################################################################
 # 3. Run the profiler