// Returns nullptr on not found or other mismatch.
// This returns a pointer to the actual node within the graph_def so as to
// avoid expensive copies.
const TensorProto* ExtractConstTensorFromGraph(const GraphDef& graph_def,
                                               const std::string& op_name) {
  const NodeDef* match_node = nullptr;
  for (const auto& node : graph_def.node()) {