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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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}')