The below code is what I come up with, but I get an error “Runtime Error: ArgumentException : Please subscribe to this symbol before adding a consolidator for it. Symbol: YM19H21”

from AlgorithmImports import *
#Futures.Indices.Dow30EMini NASDAQ100EMini SP500EMini
class BasicTemplateContinuousFutureAlgorithm(QCAlgorithm):
def Initialize(self):
self.SetStartDate(2021, 1, 1)
self.SetEndDate(2021, 12, 31)
self.ym = self.AddFuture(Futures.Indices.Dow30EMini, Resolution.Hour,
dataNormalizationMode = DataNormalizationMode.BackwardsRatio,
dataMappingMode = DataMappingMode.LastTradingDay,
contractDepthOffset= 0)
self.nq = self.AddFuture(Futures.Indices.NASDAQ100EMini, Resolution.Hour,
dataNormalizationMode = DataNormalizationMode.BackwardsRatio,
dataMappingMode = DataMappingMode.LastTradingDay,
contractDepthOffset= 0)

self.consolidator_by_symbol = {}
def OnData(self, data):
currentSymbol = self.ym.Mapped
self.Debug("test: {} ".format(currentSymbol))
if currentSymbol not in self.consolidator_by_symbol:
CountConsolidator = QuoteBarConsolidator(timedelta(hours = 2))
# CountConsolidator.DataConsolidated += self.BarHandler
self.SubscriptionManager.AddConsolidator(currentSymbol, CountConsolidator)
self.consolidator_by_symbol[currentSymbol] = CountConsolidator


def OnOrderEvent(self, orderEvent):
self.Debug("Purchased Stock: {0}".format(orderEvent.Symbol))

def OnSecuritiesChanged(self, changes):
self.Debug(f"{self.Time}-{changes}")

def BarHandler(self, sender, bar):
self.Log(f"Consolidated bar received at {self.Time}")

So What would be the correct way to do it?
Can anyone provide an example?
Thx in advance