Member nlohmann::basic_json::iterator_wrapper (reference ref) noexcept: This stream operator is deprecated and will be removed in future 4.0.0 of the library. Please use items() instead; that is, replace json::iterator_wrapper(j) with j.items().
Member nlohmann::basic_json::operator<< (basic_json &j, std::istream &i): This stream operator is deprecated and will be removed in version 4.0.0 of the library. Please use operator>>(std::istream&, basic_json&) instead; that is, replace calls like j << i; with i >> j;.
Member nlohmann::basic_json::operator>> (const basic_json &j, std::ostream &o): This stream operator is deprecated and will be removed in future 4.0.0 of the library. Please use operator<<(std::ostream&, const basic_json&) instead; that is, replace calls like j >> o; with o << j;.