Method is_begin

native/thirdpart/json/json.hpp:9202–9205

return whether the iterator can be dereferenced

    /// return whether the iterator can be dereferenced
    constexpr bool is_begin() const noexcept
    {
        return m_it == begin_value;
    }

    /// return whether the iterator is at end
    constexpr bool is_end() const noexcept