// Steps up one parallel nesting level.
  void Up();

  // Transitions nesting levels from `from` to `to`.
  void Transition(ParallelIdsMap from, ParallelIdsMap to);

  // Transitions nesting levels from the previous parallel id to `to`.
  void TransitionToParallelIdsMap(ParallelIdsMap to);

  // Transitions nesting levels from the previous parallel id to `to`.
  void TransitionToOp(Operation* to);

//    different branch values.
// `groups_from_only` is the number of group keys exclusive to `from`.
// `groups_to_only` is the number of group keys exclusive to `to`.
void CategorizeParallelIdsMap(
    ParallelIdsMap from, ParallelIdsMap to,
    int& groups_same_branch, int& groups_different_branch,
    int& groups_from_only, int& groups_to_only) {
  groups_same_branch = 0;
  groups_different_branch = 0;
  groups_from_only = 0;

      wrapped_op.emitError()
          << "Malformed " << TF::kParallelExecAnnotation << " attribute";
      return failure();
    }
    if (id_pairs.empty()) continue;

    TF::ParallelIdsMap& ids_map = op_to_parallel_ids_map[island];
    for (const auto& [group_id, branch_id] : id_pairs)
      ids_map[group_id] = branch_id;
  }
  return success();
}