None of the securities I've specified manually in the universe are iterable.

If I use `AddEquity`, I can iterate `self.Securities` but I get an error:
"During the algorithm initialization, the following exception has occurred: Framework algorithms must specify a portfolio selection model using the 'UniverseSelection' property."

Also, iterating `self.ActiveSecurities` does if nothing's there.

I avoid the error listed above if I do as the docs suggest, written below. However now neither `self.Securities` nor `self.ActiveSecurities` produces any results.

class MasterAlgo(StandardProfile):

def Initialize(self):
# Securities traded
# self.AddEquity("CRON")
symbols = [ Symbol.Create("CRON", SecurityType.Equity, Market.USA) ]
self.SetUniverseSelection( ManualUniverseSelectionModel(symbols) )

for security in self.ActiveSecurities:
self.Debug("Security: " + str(security.Key))