message: Avoid index out of range in traceable_stack
diff: @@ -4250,7 +4250,8 @@ class Graph(object):
  A context manager that specifies the default device to use for newly
  created ops.
  """
  - self._add_device_to_stack(device_name_or_function, offset=2)
  + offset = 2 if (len(tf_stack.extract_stack()) > 2) else 1
  + self._add_device_to_stack(device_name_or_function, offset=offset)
  try:
  yield
  finally:
  