Why is this returning NaN? List comprehension problem?

rolling window should just be a list of tradebars, and high and low should be floats, so I have no idea why this doesn't run properly?

in on data

for symbol, data in self.symbolData.items():
           price = self.Securities[symbol].Price
           stdbarDelta = (2 * (np.std(list([(x.High - x.Low) for x in data.windowonedayTradeBar]))))
           #self.Debug(f'{symbol} {stdbarDelta} test')

class SymbolData:
   def __init__(self, algorithm, symbol):
       
       #ten minute bars for window
       tenMinuteConsolidator = TradeBarConsolidator(timedelta(minutes=10))
       self.subscribe = algorithm.SubscriptionManager.AddConsolidator(symbol, tenMinuteConsolidator)
       #window for 39 ten minute bars of consolidated minute data
       self.windowonedayTradeBar = RollingWindow[TradeBar](39)
       tenMinuteConsolidator.DataConsolidated += self.barHandler10min

def barHandler10min(self, sender, updated):
       pass