Function begin

examples/server/json.hpp:21936–21941

@brief returns an iterator to the first element @sa https://json.nlohmann.me/api/basic_json/begin/

    /// @brief returns an iterator to the first element
    /// @sa https://json.nlohmann.me/api/basic_json/begin/
    iterator begin() noexcept
    {
        iterator result(this);
        result.set_begin();
        return result;
    }

    /// @brief returns an iterator to the first element
    /// @sa https://json.nlohmann.me/api/basic_json/begin/