absl::optional<std::vector<std::unique_ptr<ParallelTensor>>>
      maybe_parallel_results(
          parallel_device.Execute(context, parallel_inputs, operation_name,
                                  attributes, expected_max_outputs, status));
  if (!maybe_parallel_results.has_value()) return result;
  std::vector<std::unique_ptr<ParallelTensor>> parallel_results(
      std::move(maybe_parallel_results.value()));

    // 'read0_maybe_with_graph_error' op having a requested device `dev2_name`.
    // During execution:
    //   * task:0 processes main function `VariableAddFunctionWithGraphError`
    //     and places the 'read0_maybe_with_graph_error' op on task:2
    //   * task:0 partitions the main function with a subgraph containing
    //     'read0_maybe_with_graph_error' sent to task:2