// representation of a `ModuleOp` containing a single function `@main`.
  // Returns `failure` iff there is no `@main` or no such operation is found in
  // `@main`.
  template <typename OpT>
  FailureOr<OpT> FindFirstOpFromMainFunc(ModuleOp module_op) {
    func::FuncOp main_func_op = FindMainFuncOp(module_op);
    if (main_func_op == nullptr) return failure();

    auto ops = main_func_op.getOps<OpT>();
    if (ops.empty()) return failure();

  const OwningOpRef<ModuleOp> module_op =
      ParseModuleOpString(kXlaCallModuleOpWithPerTensorQuantizedConvolution);
  ASSERT_TRUE(module_op);

  const FailureOr<TF::XlaCallModuleOp> xla_call_module_op =
      FindFirstOpFromMainFunc<TF::XlaCallModuleOp>(*module_op);
  ASSERT_TRUE(succeeded(xla_call_module_op));

  const std::unique_ptr<OpQuantSpec> op_quant_spec =
      GetStableHloOpQuantSpec(*xla_call_module_op);

  const OwningOpRef<ModuleOp> module_op =
      ParseModuleOpString(kXlaCallModuleOpWithQuantizationMethodAttr);
  ASSERT_TRUE(module_op);

  FailureOr<TF::XlaCallModuleOp> xla_call_module_op =
      FindFirstOpFromMainFunc<TF::XlaCallModuleOp>(*module_op);
  ASSERT_TRUE(succeeded(xla_call_module_op));

  // Test that `GetQuantizationMethodOrDefault` returns a valid `Method`
  // corresponding to `"no_quantization {}"`.