message: Avoid infinite loop in uses_keras_history
diff: @@ -310,6 +310,9 @@ def uses_keras_history(tensors):
  while tensors_to_check:
  new_tensors_to_check = []
  for tensor in tensors_to_check:
  + if id(tensor) in checked_tensors:
  + continue
  +
  checked_tensors.add(id(tensor))
  if getattr(tensor, '_keras_history_checked', None) is not None:
  @@ -318,9 +321,7 @@ def uses_keras_history(tensors):
  return True
  try:
  - for t in tensor.op.inputs:
  - if id(t) not in checked_tensors:
  - new_tensors_to_check.append(t)
  + new_tensors_to_check.extend(tensor.op.inputs)
  except AttributeError:
  # In case `tensor` is a Variable created in an Eager context.
  pass
  