how do you use benchmark::RegisterBenchmark but with a fixtured benchmark that was previously defined using BENCHMARK_DEFINE_F(FixtureClass, MethodName)[BUG] about benchmark HOT 5 OPEN

BENCHMARK_DEFINE_F(FixtureClassName, BM_Func)
(::benchmark::State& state) {
  for (auto _ : state) {
     [..... bench logic here .....]
  }
}

int main(int argc, char** argv){
  // Some arg parsing logic here (verified to work just fine)
  benchmark::Initialize(&rem_argv_len, rem_argv_c.data());
  benchmark::RegisterBenchmark("SomeArbitraryName", FixtureClassName_BM_Func_Benchmark)->Arg(0); // checked what the macro resolved to and it puts "_Benchmark" at the end and passing here dummy 0 in Arg but it represents what I would like to do
  benchmark::RunSpecifiedBenchmarks();
  benchmark::Shutdown();
}

class FixtureClass : public benchmark::Fixture {
 public:
  void SetUp(const ::benchmark::State& state) override {}
  void TearDown(const ::benchmark::State& state) override {}
};

class FixtureClass_BM_Func_Benchmark : public FixtureClass {
 public:
  FixtureClass_BM_Func_Benchmark() { this->SetName("FixtureClass" "/" "BM_Func"); }
 protected:
  void BenchmarkCase(::benchmark::State&)         override; };
  void FixtureClass_BM_Func_Benchmark::BenchmarkCase(::benchmark::State& state) {
    int i = 0;
    for (auto _ : state) {
      benchmark::DoNotOptimize(i += 1);
    }
  }

static ::benchmark::internal::Benchmark* benchmark_uniq_2FixtureClass_BM_Func_Benchmark __attribute__((unused)) =
  (::benchmark::internal::RegisterBenchmarkInternal(new FixtureClass_BM_Func_Benchmark()))->Arg(0);