message: Fixed a NameError in backprop.batch_jacobian
diff: @@ -1123,7 +1123,7 @@ class GradientTape(object):
  """
  target_shape = target.shape
  if target_shape.rank is None:
  - dim = Dimension(None)
  + dim = tensor_shape.Dimension(None)
  else:
  dim = target_shape.dims[0]
  if not (target_shape.with_rank_at_least(2) and
  