code: def startTicker(self, reqId, contract, tickType):
          
          ticker = self.tickers.get(id(contract))
          if not ticker:
              ticker = Ticker(
                  contract=contract, ticks=[], tickByTicks=[],
                  domBids=[], domAsks=[], domTicks=[])
              self.tickers[id(contract)] = ticker
          self.reqId2Ticker[reqId] = ticker
          self._reqId2Contract[reqId] = contract
          self.ticker2ReqId[tickType][ticker] = reqId
          return ticker
docs: Start a tick request that has the reqId associated with the contract.
          Return the ticker.