// Collect the control operands separately, they will be held by the island.
  mlir::SmallVector<mlir::Value, 8> control_operands;

  for (const auto* input_edge : in_edges) {
    const Node& input_node = *input_edge->src();
    if (input_node.IsSource()) {
      if (in_edges.size() != 1) {
        return errors::FailedPrecondition(
            "The node has other inputs besides the _Source node");

    return -1;
  }
  return iter->second.second - iter->second.first;
}

TF_Output TF_OperationInput(TF_Input oper_in) {
  const tensorflow::Edge* edge;
  Status s = oper_in.oper->node.input_edge(oper_in.index, &edge);
  if (!s.ok()) {
    return {nullptr, -1};
  }

  return {ToOperation(edge->src()), edge->src_output()};
}