message: [tpu_driver] Add missing namespace to fix OS build
diff: @@ -95,7 +95,7 @@ PyTpuClient::PyTpuClient(std::string platform_name,
  devices_(std::move(devices)),
  process_index_(process_index) {
  for (const std::shared_ptr<PjRtDevice>& device : devices_) {
  - down_cast<TpuDevice*>(device.get())->set_tpu_client(this);
  + tensorflow::down_cast<TpuDevice*>(device.get())->set_tpu_client(this);
  CHECK(id_to_device_.insert({device->id(), device}).second)
  << "Duplicate device id: " << device->id();
  