<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def abort_io(self, iocb, err):
 """Forward the abort downstream."""

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

        # make sure we're being notified of an abort request from
        # the iocb we are chained from
        if iocb is not self.ioChain:
            raise RuntimeError("broken chain")

        # call my own Abort(), which may forward it to a controller or
        # be overridden by IOGroup
        self.abort(err)