I am trying to iterate throught he symbols of the universe (created manually or with a Fundamental function). When I try to find the Active securities then I find an empty list.  I would expect to see a value of one for universe_len below and a larger number when using the function:  self.SetUniverseSelection(FineFundamentalUniverseSelectionModel(self.SelectCoarse,self.SelectFine))

How should I populate a list of assets in the created universe with ActiveSecurities?

from QuantConnect import *

from QuantConnect.Algorithm import QCAlgorithm

class BootCampTask(QCAlgorithm):

    def Initialize(self):

        self.SetStartDate(2019, 8, 5)
        self.SetEndDate(2019, 8, 23)
        self.UniverseSettings.Resolution = Resolution.Daily
        symbols = [ Symbol.Create("SPY", SecurityType.Equity, Market.USA) ]
        universe_len = len([x.Symbol for x in self.ActiveSecurities])