if (auto graph = dyn_cast<tf_executor::GraphOp>(op)) {
    if (port.size() == 1)
      return ComputeOutputComponent(
          ValuePort(graph.GetFetch().getFetches()[port[0]]), values);
    return nullptr;
  }

  if (auto island = dyn_cast<tf_executor::IslandOp>(op)) {
    if (port.size() == 1)
      return ComputeOutputComponent(
          ValuePort(island.GetYield().getFetches()[port[0]]), values);
    return nullptr;
  }