for h := range hosts {
		if ip := net.ParseIP(h); ip != nil {
			template.IPAddresses = append(template.IPAddresses, ip)
		} else {
			template.DNSNames = append(template.DNSNames, h)
		}
	}

	template.IsCA = true
	template.KeyUsage |= x509.KeyUsageCertSign

	derBytes, err := x509.CreateCertificate(crand.Reader, &template, &template, publicKey(priv), priv)
	if err != nil {

    ASSERT_NE(*op, nullptr);
  }

  FunctionDef fdef() {
    tensorflow::FunctionDef fdef;
    EXPECT_TRUE(GetFunctionDef(func_, &fdef));
    return fdef;
  }

  // logging utility
  template <class Container>
  string ToString(const Container& v) {
    std::stringstream ss;
    ss << "{";
    size_t i = 0;
    for (const auto& e : v) {
      if (i != 0) {
        ss << ", ";
      }