Method extract

src/mgr/MgrMapCache.h:162–162

  }
  void insert(std::string_view k, Value v) { CacheImp::insert(k, v); }
  bool extract(std::string_view k, Value* out) noexcept { return CacheImp::extract(k, out); }
  void erase(std::string_view k) noexcept { Value v{}; (void)CacheImp::extract(k, &v); }
  void clear() noexcept { CacheImp::clear(); }
private: