Hello, when I launch this algorithm it returns me an error.However I don't see what can be wrong.Can Someone help me please


Thank You 

class DynamicHorizontalChamber(QCAlgorithm):

def Initialize(self):
self.SetStartDate(2019, 1, 7)
self.SetEndDate(2019, 4, 1)
self.UniverseSettings.Resolution = Resolution.Daily
self.averages = { }

def SelectionFunction(self, universe):
selected = []
universe = sorted(universe, key=lambda c: c.DollarVolume, reverse=True)
universe = [c for c in universe if c.Price > 100][:100]

for coarse in universe:
symbol = coarse.Symbol

if symbol not in self.averages:

history = self.History(symbol, 200, Resolution.Daily)

self.averages[symbol] = Selection(history)

self.averages[symbol].update(self.Time, coarse.AdjustedPrice)

if self.averages[symbol].is_ready() and self.averages[symbol].stt < 20:

return selected[100:]

def OnSecuritiesChanged(self, changes):
self.changes = changes
self.Log(f"OnSecuritiesChanged({self.Time}):: {changes}")

for security in self.changes.RemovedSecurities:
if security.Invested:

for security in self.changes.AddedSecurities:
self.SetHoldings(security.Symbol, 0.10)

class Selection():
def __init__(self,history):

self.stt = StandardDeviation(200)
for bar in history.itertuples():

def is_ready(self):
return self.stt.IsReady

def update(self, time, price):