If I add my securities

        self.AddEquity("SPY")
        self.AddEquity("BAC")
        self.AddEquity("IBM")

They are added to the hidden(correct name?) universe. I'd like to create a list of securities built off of my subscribed universe. The ultimate goal is to be able to use 

self.AddUniverse(self.Universe.DollarVolume.Top(50))

and then create a list off of this universe.

 

Thank you.