void archive(archive_node& n) const override;
/** Read (a.k.a. deserialize) object from archive. */
void read_archive(const archive_node& n, lst& syms) override;
void archive(archive_node& n) const override;
/** Read (a.k.a. deserialize) object from archive. */
void read_archive(const archive_node& n, lst& syms) override;