} else if (attr.first == "N") {
      if (attr.second.i() == n) {
        found_n = true;
      } else {
        return false;
      }
    }
  }
  return found_t && found_n;
}

bool IsNeg(const tensorflow::NodeDef& node_def, const string& input) {
  return node_def.op() == "Neg" && node_def.name() == "neg" &&
         node_def.input_size() == 1 && node_def.input(0) == input;
}