Hi all - can a rolling window be used to store and recall multiple symbols' histories?

I understand that:

self.window.Add(data['AAPL']) Bar = self.window[i]

will index the ith previous day, but below, the index references the symbol, not the history:

self.window.Add(data['AAPL']) self.window.Add(data['IBM']) IBMBar = self.window[0] AAPLBar = self.window[1]

I've tried pandas-esque multiple indexing variations of e.g. self.window['IBM'][1] or self.window[0][1] but no luck. 

I'd like to store all ticker histories in a single window if possible.

Thanks in advance!