Assert that TracingContext is available when set_example_value is called (#124284)

Summary:
Signed-off-by: Edward Z. Yang <[email protected]>

X-link: pytorch/pytorch#124284
Approved by: https://github.com/Chillee
ghstack dependencies: #124105, #124059, #124176, #124283

Reviewed By: jeanschmidt

Differential Revision: D56408587

Pulled By: ezyang

fbshipit-source-id: 00772f4e4dd2b323116861626570c04591fbf7ec

Author: ezyang

userbenchmark/dynamo/dynamobench/_dynamo/utils.py

@@ -95,6 +95,7 @@
 import torch.utils._pytree as pytree
 from torch import fx
 from torch._dispatch.python import enable_python_dispatcher
+from torch._guards import TracingContext
 from torch._subclasses.meta_utils import is_sparse_compressed
 from torch._utils_internal import log_compilation_event
 
@@ -1152,6 +1153,7 @@ def set_example_value(node, example_value):
     # this to accurately reflect what the state of the value was at the time
     # the program was traced).
     node.meta["example_value"] = example_value
+    assert TracingContext.try_get() is not None
 
 
 def _get_fake_tensor(vt):