Method operator[]

tools/flatbuffers_backed_impl.cc:64–68

      : arena_(arena), list_(list), schema_(schema), object_(object) {}
  int size() const override { return list_ ? list_->size() : 0; }
  CelValue operator[](int index) const override {
    auto value = list_->Get(index);
    return CelValue::CreateMap(google::protobuf::Arena::Create<FlatBuffersMapImpl>(
        arena_, *value, schema_, object_, arena_));
  }

 private:
  google::protobuf::Arena* arena_;