correct __slots__ for Valve.
correct __slots__ for Valve.

mwutzke/faucet,shivarammysore/faucet,mwutzke/faucet,trungdtbk/faucet,gizmoguy/faucet,faucetsdn/faucet,REANNZ/faucet,anarkiwi/faucet,faucetsdn/faucet,shivarammysore/faucet,anarkiwi/faucet,trungdtbk/faucet,REANNZ/faucet,trentindav/faucet,trentindav/faucet,gizmoguy/faucet