luggage locker in metro station

I am travelling from Hangzhou to shanghai(pudong) to catch a flight in the mid night to India. I am planning to come by high speed train and take metro subway line2. I thought if I can keep my luggage in metro station, I could roam around the city till night. Please let me know, if there is any such facility in any of the metro stations.

I know there is facility in Pudong airport. But I don't want to go all the way to airport and come back again for sight seeing. Please advice.