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