std::string serialize(SerializeFormat format, const Extensible* container, void* item) const;
intptr_t get(const Extensible* container) const;
intptr_t set(Extensible* container, intptr_t value);
std::string serialize(SerializeFormat format, const Extensible* container, void* item) const;
intptr_t get(const Extensible* container) const;
intptr_t set(Extensible* container, intptr_t value);