Unsubscribe from market depth data.

        Args:
            contract: The exact contract object that was used to
                subscribe with.

def cancelMktDepth(self, contract: Contract, isSmartDepth=False):
        """
        Unsubscribe from market depth data.

        Args:
            contract: The exact contract object that was used to
                subscribe with.
        """
        ticker = self.ticker(contract)
        reqId = self.wrapper.endTicker(ticker, 'mktDepth')
        if reqId:
            self.client.cancelMktDepth(reqId, isSmartDepth)
        else:
            self._logger.error(
                f'cancelMktDepth: No reqId found for contract {contract}')