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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 _prep_jid(self, clear_load, extra):
        '''
        Return a jid for this publication
        '''
        # the jid in clear_load can be None, '', or something else. this is an
        # attempt to clean up the value before passing to plugins
        passed_jid = clear_load['jid'] if clear_load.get('jid') else None
        nocache = extra.get('nocache', False)

        # Retrieve the jid
        fstr = '{0}.prep_jid'.format(self.opts['master_job_cache'])
        try:
            # Retrieve the jid
            jid = self.mminion.returners[fstr](nocache=nocache,
                                               passed_jid=passed_jid)
        except (KeyError, TypeError):
            # The returner is not present
            msg = (
                'Failed to allocate a jid. The requested returner \'{0}\' '
                'could not be loaded.'.format(fstr.split('.')[0])
            )
            log.error(msg)
            return {'error': msg}
        return jid