pack off then on before pushback(B777)

[triptobaek]

Just before the B777 push back (before the before start procedure), it takes about a few seconds for the pack to turn off and on again, and I don't think this is for engine start.
Does anyone know why?

[LME (GOD)]

It's a function of the autostart. (unless the crew have something else in check pushback checklist which requires packs off?)