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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 chain_callback(self, iocb):
 """Callback when this iocb completes."""

        if _debug: IOChainMixIn._debug("chain_callback %r", iocb)

        # if we're not chained, there's no notification to do
        if not self.ioChain:
            return

        # refer to the chained iocb
        iocb = self.ioChain

        try:
            if _debug: IOChainMixIn._debug("    - decoding")

            # let the derived class transform the data
            self.decode()

            if _debug: IOChainMixIn._debug("    - decode complete")
        except:
            # extract the error and abort
            err = sys.exc_info()[1]
            if _debug: IOChainMixIn._exception("    - decoding exception: %r", err)

            iocb.ioState = ABORTED
            iocb.ioError = err

        # break the references
        self.ioChain = None
        iocb.ioController = None

        # notify the client
        iocb.trigger()