std::vector<Operation*> control_nodes;
  for (const auto& item : llvm::enumerate(*block)) {
    if (llvm::isa<mlir::TFL::ControlNodeOp>(item.value())) {
      control_nodes.push_back(&item.value());
      control_nodes_at.try_emplace(&item.value(), item.index());
    }
  }

  for (auto outer_op : control_nodes) {
    auto control_node_op = dyn_cast<mlir::TFL::ControlNodeOp>(outer_op);