message: Remove Raises documentation on imperative_grads for ValueErrror not raised.
diff: @@ -51,11 +51,6 @@ def imperative_grad(
  Raises:
  RuntimeError: if something goes wrong.
  - ValueError: if there is no sequence of differentiable operations connecting
  - a source and any target Tensor. This can happen either if the target is
  - not computed based on the source, if the tracing was set up incorrectly,
  - or if only non-differentiable functions of the source were used in the
  - computation of target.
  """
  return pywrap_tensorflow.TFE_Py_TapeGradient(
  tape._tape, # pylint: disable=protected-access
  