Getting Historical Stock Price on a list of stocks

First attempt at this is throwing an error:

Runtime Error: 'SimpleMovingAverage' object has no attribute 'Symbol'

  at SmaUpdated

    self.window[sender.symbol].Add(updated) 

#region imports
from AlgorithmImports import *
#endregion
from QuantConnect.Data.Market import TradeBar



class RollingWindowAlgorithm(QCAlgorithm):
    '''Example on how to use Rolling Window with bar and indicator'''


    def Initialize(self):
        '''Initialise the data and resolution required, as well as the cash and start-end dates for your algorithm. All algorithms must initialized.'''
   
        self.SetStartDate(2013,10,1)  #Set Start Date
        self.SetEndDate(2013,11,1)    #Set End Date
        self.SetCash(100000)           #Set Strategy Cash
        # Find more symbols here: http://quantconnect.com/data
   
        # Define the list of stocks you want to trade
        self.symbols = ["AAPL", "GOOGL", "FB", "AMZN"]


        # Add all the stocks in the list to the algorithm
        for symbol in self.symbols:
            self.AddEquity(symbol, Resolution.Daily)


    # Creates a Rolling Window indicator to keep the 2 TradeBar
        self.window = {}
        for symbol in self.symbols:
            self.window[symbol] = RollingWindow[TradeBar](2)    # For other security types, use QuoteBar


    # Creates an indicator and adds to a rolling window when it is updated        
        for symbol in self.symbols:
            self.SMA(symbol, 5).Updated += self.SmaUpdated
            self.window[symbol] = RollingWindow[IndicatorDataPoint](5)



    def SmaUpdated(self, sender, updated):
        for symbol in self.symbols:
            self.window[sender.symbol].Add(updated)



    def OnData(self, data):


        for symbol in self.symbols:
            # Add TradeBar for each stock in rolling window
            self.window[symbol].Add(data[symbol])


            # Wait for windows to be ready.
            if not (self.window[symbol].IsReady and self.window[symbol].IsReady): continue


            currBar = self.window[symbol][0]                     # Current bar had index zero.
            pastBar = self.window[symbol][1]                     # Past bar has index one.
            self.Log("{0} - Price: {1} -> {2} ... {3} -> {4}".format(symbol, pastBar.Time, pastBar.Close, currBar.Time, currBar.Close))


            currSma = self.window[symbol][0]                     # Current SMA had index zero.
            pastSma = self.window[symbol][self.window[symbol].Count-1]   # Oldest SMA has index of window count minus 1.
            self.Log("{0} - SMA:   {1} -> {2} ... {3} -> {4}".format(symbol, pastSma.Time, pastSma.Value, currSma.Time, currSma.Value))


            if not self.Portfolio.Invested and currSma.Value > pastSma.Value:
                self.SetHoldings(symbol, 1)

And solved it: