message: Fix gradient of nccl_ops
diff: @@ -63,12 +63,12 @@ def _all_sum_grad(op, grad):
  Raises:
  LookupError: If `reduction` is not `sum`.
  """
  - if op.get_attr('reduction') != 'sum':
  + if op.get_attr('reduction') != b'sum':
  raise LookupError('No gradient defined for NcclAllReduce except sum.')
  _check_device(grad, expected=op.device)
  num_devices = op.get_attr('num_devices')
  - shared_name = op.get_attr('shared_name') + '_grad'
  + shared_name = op.get_attr('shared_name') + b'_grad'
  with ops.device(op.device):
  return gen_nccl_ops.nccl_all_reduce(
  @@ -162,7 +162,7 @@ def _reduce_sum_grad(op, grad):
  Raises:
  LookupError: If the reduction attribute of op is not `sum`.
  """
  - if op.get_attr('reduction') != 'sum':
  + if op.get_attr('reduction') != b'sum':
  raise LookupError('No gradient defined for NcclReduce except sum.')
  _check_device(grad, expected=op.device)
  