When praying salah before the "Assalamu alaikum wa rahmatullah" and turning your head towards right and left shoulder what is the fourth Tashahhud to be recited following At-Tahiyyatu, Allahumma salli 'ala, Allahumma barik'ala...

I have been recting Allahumma inna nastainuka, wanastagfirukka... is this valid?