Cancel streaming market data for contract
        https://www.interactivebrokers.com/en/software/api/apiguide/java/cancelmktdepth.htm

def cancelMarketDepth(self, contracts=None):
        """
        Cancel streaming market data for contract
        https://www.interactivebrokers.com/en/software/api/apiguide/java/cancelmktdepth.htm
        """
        if contracts == None:
            contracts = list(self.contracts.values())
        elif not isinstance(contracts, list):
            contracts = [contracts]

        for contract in contracts:
            tickerId = self.tickerId(self.contractString(contract))
            self.ibConn.cancelMktDepth(tickerId=tickerId)