There seems to be a problem with the solution to this task. I wrote code but then I got an error saying 'Runtime Error: NameError : name 'symbol' is not defined NameError : name 'symbol' is not defined (Open Stacktrace)'

When comparing my code to the solution, it was identical. I then ran the code in the solution and still got the same error. Here is the code from the solution to this task:


class MySectorWeightingPortfolioConstructionModel(EqualWeightingPortfolioConstructionModel):

    def __init__(self, rebalancingParam = Resolution.Daily):
        self.symbolBySectorCode = dict()

    def OnSecuritiesChanged(self, algorithm, changes):
        #1. When new assets are added to the universe, save the MorningStar sector code for each security to the variable sectorCode
        for security in changes.AddedSecurities:
            sectorCode = security.Fundamentals.AssetClassification.MorningstarSectorCode
            # 2. If the sectorCode is not in the self.symbolBySectorCode dictionary, save the values as a list 
            # and append the security symbol as the value in the self.symbolBySectorCode dictionary 
            if sectorCode not in self.symbolBySectorCode:
                self.symbolBySectorCode[sectorCode] = list()
        #3. For securities that are removed, save their MorningStar sector code to sectorCode
        for security in changes.RemovedSecurities:
            sectorCode = security.Fundamentals.AssetClassification.MorningstarSectorCode
            #4. If the saved sectorCode is in the self.symbolBySectorCode dictionary, save the security's symbol object to symbol 
            if sectorCode in self.symbolBySectorCode:
                if symbol in self.symbolBySectorCode[sectorCode]:
        # We use the super() function to avoid using the base class name explicity
        super().OnSecuritiesChanged(algorithm, changes)