Method operator--

lesson6-Segmentation/json.hpp:11122–11127

! @brief post-decrement (it--) @pre The iterator is initialized; i.e. `m_object != nullptr`. */

    @pre The iterator is initialized; i.e. `m_object != nullptr`.
    */
    iter_impl const operator--(int)
    {
        auto result = *this;
        --(*this);
        return result;
    }

    /*!
    @brief pre-decrement (--it)