So, for the following code:

class ForexTemplateAlgorithm(QCAlgorithm): def Initialize(self): self.SetCash(100000) self.SetStartDate(2018,1,1) self.SetEndDate(datetime.now() - timedelta(1)) self.signs = [ "USDCAD", "EURUSD", "USDCHF", "EURGBP", "GBPUSD", "USDJPY", ] self.symbols = [Symbol.Create(x, SecurityType.Forex, Market.Oanda) for x in self.signs] self.UniverseSettings.Resolution = Resolution.Daily self.AddUniverseSelection(ManualUniverseSelectionModel(self.symbols)) self.SetAlpha(RsiAlphaModel()) self.SetAlpha(EmaCrossAlphaModel()) self.SetAlpha(MacdAlphaModel()) self.SetPortfolioConstruction(MeanVarianceOptimizationPortfolioConstructionModel()) self.SetRiskManagement(MaximumDrawdownPercentPerSecurity(0.02)) self.SetExecution(ImmediateExecutionModel())

I get the following errors:
`Runtime Error: An item with the same key has already been added. Key: 11/03/2017 20:00:00 (Open Stacktrace)`

I am assuming it's because I'm trying to analyze Forex data but the MeanVarianceOptimizationPortfolioConstructionModel is calculating returns on 252 trading days as opposed to daily for Forex as shown in this code: 

https://github.com/QuantConnect/Lean/blob/master/Algorithm.Framework/Portfolio/MeanVarianceOptimizationPortfolioConstructionModel.py#L173


My question is, what should I do to modify the returns formula for the MeanVarianceOptimizationPortfolioConstructionModel code so it's compatible with Forex. Do I calculate returns over 365 days instead?

Thank you for your help! Best wishes.