message: [tf.data] Fix a bug in prefetch dataset serialization logic.
diff: @@ -100,9 +100,13 @@ class PrefetchDatasetOp::Dataset : public DatasetBase {
  TF_RETURN_IF_ERROR(b->AddScalar(buffer_size_, &buffer_size));
  AttrValue slack_period_attr;
  b->BuildAttrValue(slack_period_, &slack_period_attr);
  - TF_RETURN_IF_ERROR(b->AddDataset(
  - this, {input_graph_node, buffer_size},
  - {std::make_pair(kSlackPeriod, slack_period_attr)}, output));
  + AttrValue legacy_autotune_attr;
  + b->BuildAttrValue(legacy_autotune_, &legacy_autotune_attr);
  + TF_RETURN_IF_ERROR(
  + b->AddDataset(this, {input_graph_node, buffer_size},
  + {std::make_pair(kSlackPeriod, slack_period_attr),
  + std::make_pair(kLegacyAutotune, legacy_autotune_attr)},
  + output));
  return Status::OK();
  }
  