// We pre-allocate the array of operands and populate it using the
// `output_name_to_position` and `control_output_to_position` populated
// previously.
SmallVector<Value> ret_vals(func.ret_size() + func.control_ret_size(),
                            Value());
for (const auto& ret_val : func.ret()) {
  auto position = output_name_to_position.find(ret_val.first);
  if (position == output_name_to_position.end())
    return InvalidArgument(
        "Can't import function, returned value references unknown output "
        "argument ",
        ret_val.first);
  ret_vals[position->second] =
      value_manager.GetValueOrCreatePlaceholder(ret_val.second);
}
for (const auto& ret_val : func.control_ret()) {
  auto position = control_output_to_position.find(ret_val.first);
  if (position == control_output_to_position.end())
    return InvalidArgument(
        "Can't import function, returned value references unknown output "
        "argument ",
        ret_val.first);
  Value result = value_manager.GetValueOrCreatePlaceholder(
      (Twine("^") + ret_val.second).str());

// Process every node and create a matching MLIR operation
for (const NodeDef& node : nodes) {
  if (node.op().empty()) return InvalidArgument("empty op type");
  OperationState state(unknown_loc, absl::StrCat("tfg.", node.op()));
  // Fetch the inputs, creating placeholder if an input hasn't been visited.
  for (const std::string& input : node.input())
    state.operands.push_back(
        value_manager.GetValueOrCreatePlaceholder(input));